Depth of Field Table Depth of Field Table To print the background color with the chart, enable background color printing in your browser. Hyperfocal, near, and far distances are calculated using these equations. Circles of confusion for digital cameras are listed here. Depth of Field Definition Depth of field refers to the section of a photograph that appears to be in sharp focus. Night and Low-Light Photography Workshop , Alan Hess, 2011 When an object is in focus, everything from a certain distance in front of the object to a certain distance behind the object will also be in reasonably sharp focus. This distance from front to back that will be in reasonably sharp focus is called the depth of field. How to Use Your Camera, New York Institute of Photography, 2000. Hyperfocal Distance Definition If you set the camera's focus to the hyperfocal distance, your depth of field will extend from half of the hyperfocal distance to infinity—a much deeper depth of field. Complete Digital Photography , Ben Long, 2012. Hyperfocal is a combination of distance and aperture that produces the sharpest image and greatest depth of field possible for a given lens.

How to Blur Backgrounds with a Compact Camera - CreativePro.com Home » How-Tos » How to Blur Backgrounds with a Compact Camera How to Blur Backgrounds with a Compact Camera 0 Comments In photography, blurring the background helps draw attention to the subject of the photo. It’s not hard to do with a digital SLR camera because of the digital sensor’s or film frame’s size (also called the format), but what if all you have is the small-format digital camera in your pocket? You can blur the background with almost any camera if you can control the factors that affect what’s in focus. And when you shop for a compact digital camera, you can look for certain features that make it easier to blur backgrounds. In some photos almost everything appears to be in reasonably sharp focus, from nearby objects to distant objects. In other photos only a thin slice of the total depth of the scene (at the actual focus distance) appears sharp, and the rest is visibly blurred out of focus. The range of the distance that’s in focus is called the depth of field. It starts from the focus point (the distance of your subject), with the range of acceptable focus extending in front of and behind your subject.

The photographic techniques for using depth of field to blur the background are the same no matter what kind of camera you have, but the limitations of small-format compact cameras make you work harder than you would with a camera with a larger frame format. Move the subject closer to you and farther from the background Make the camera-to-subject distance as small as possible, and make the subject-to-background distance as large as possible. This shifts depth of field toward you and away from the background so that it blurs. Controlling this ratio of distances is helpful when your compact camera’s minimum depth of field is relatively deep, and it’s the only technique in this article that you can use with a typical smartphone camera. It’s also one reason why macro photos have such shallow depth of field: You’re very close to the subject, so the range that’s in focus is much closer to you than to the background. The pair of warning signs is on two entrance doors open several feet apart in parallel. I can’t move the background door farther away, but in the second photo I move closer to the foreground sign. That’s enough to visibly blur the background sign. No camera settings were changed.

Open the lens aperture as much as possible As you open the lens aperture wider, you narrow the depth of field. That’s why, all other things being equal, a lens set to f/2 has much shallower depth of field than a lens set to f/16. While every experienced SLR photographer knows this, what’s different today is that more compact digital cameras have a lens aperture that you can manually set to f/2 or less. If blurring backgrounds with a compact camera is important to you, shop for a camera with that capability. (Remember, a lower f/stop value indicates a larger aperture.) The first photo has an aperture value of f/2.8. Opening up to f/1.4 blurs the background much more in the second photo. But this is only possible because the compact camera I used is capable of f/1.4 and manual aperture control, as shown below. Use a neutral density filter to avoid overexposure There’s a potential problem with opening the aperture all the way to blur the background. In bright light, such as a sunny day, a lens at maximum aperture may let in so much light that the camera can’t avoid overexposure.

(On many compact cameras, the range of available shutter speeds, apertures, and ISO speeds is limited compared to an SLR camera.) To counter this, some digital compact cameras have a built-in neutral density (ND) filter that that you can switch on and off. A neutral density filter physically limits incoming light for a scene that would otherwise be too bright for the camera to achieve the exposure you want. The first photo has an aperture value of f/2.8. In the second photo, opening to f/1.4 increases background blur, but it contains overexposed highlights because the camera is at the limits of its shutter speed and ISO speed. Turning on the neutral density filter solves the problem in the third photo. On this compact camera, pressing the ND/Focus dial at the top turns on the ND filter, as shown by the ND indicator at the bottom. If your digital compact camera doesn’t have a ND filter built in you might be able to attach one, but not all compact cameras let you attach a filter as easily as on an SLR camera lens. Remember to stop using the ND filter when you’re no longer in very bright light, because you usually want the camera to have as much light as it can get.

Zoom in When you use a lens with a longer focal length, the narrower angle of view magnifies out-of-focus areas. You may be able to take advantage of this effect if your compact camera has a zoom lens. Zoom in on your subject and the background blur will appear to increase. This is one reason portrait photographers tend to prefer longer focal lengths. There’s a misconception that longer focal length directly reduces depth of field. Actually, it doesn’t. What you really see is the same out-of-focus background enlarged due to the narrower angle of view. If you take the same photo with a longer focal length and a shorter focal length, and you crop the shorter focal length photo to make the subject the same size as it is in the longer focal length photo, you’ll see that the actual depth of field is the same. When it comes to controlling depth of field, the traditional gap between SLR cameras and compact cameras has been narrowed by advanced digital compact cameras with features like a manually controlled large aperture lens and a built-in neutral density filter. Some compact cameras even have sensor sizes that are closer to that of an SLR.

These features can help you can more easily blur backgrounds under a wider range of conditions than with a typical compact camera, especially when you combine those features with traditional depth-of-field techniques. Missing Pages: Depth of Field - photo.net Missing Pages: Depth of Field Tips for Using Your Camera Creatively by Jon Sienkiewicz , April 2009 (updated June 2010) Introduction | I: ISO Setting | II: Program AE | III: Aperture & Shutter Priority | IV: White Balance | V: Depth of Field | VI: Bracketing | VII: Megapixels | VIII: Flash Modes The Missing Pages column is a collection of all of the information that should have been included in your camera’s Owner’s Manual—but somehow got left out. This is a hybrid assortment of short articles that delivers the know-how you need to derive the maximum enjoyment—and creative expression—from your equipment. It’s sort of a juiced-up User Guide for creative people who are not necessarily technical. Each part will teach you how to use one of the camera features or functions that you previously ignored or left set on Auto. And each will include a Creative Project so that you can try some scripted experimentation.

We will explain complex technical subject matter a way that everyone can understand. And if you happen to be a technical expert yourself, we’re including “Nerds Only” sidebars just for you. That way you can dig in deep—or just straddle the edges—of the technological stuff. It’s your decision. Installment V: Depth of Field Definition: The area in front of and behind the point of focus that also appears to be sharp. You’ve seen the classic portrait that depicts a smiling face in sharp focus floating over a blurred and obscured background, as in the photo below. The subject appears to pop right off the page. And you’ve seen hundreds of shots of landscapes where the animals in the foreground are as sharp and clear as the mountains behind them. How can you control exactly what’s in focus and what’s not—particularly with an autofocus camera? Jon Sienkiewicz The phenomenon at work here is called Depth of Field (DOF). Because it’s predictable, reproducible and measurable we can use it to our best advantage. And since it’s been studied by scientists and optical engineers for centuries, we know a lot about it.

DOF increases as the diameter of the aperture decreases; in other words, a smaller f/stop (like f/16) generates greater DOF than a larger f/stop (like f/2.8). Sometimes people confuse this with sharpness but the two are quite different. In fact, using a very small aperture can rob you of sharpness. You can learn more about that by reading the Nerd’s Only section below. One way to control DOF is by using the right aperture, the aperture that delivers the amount of DOF that you’re after. Shooting in Program or Auto Exposure mode surrenders control over the f/stop, so your camera must be set on Aperture Priority or Manual if you wish to control DOF. Some lenses have a Depth of Field scale printed on the barrel. It looks like a symmetrical set of hash marks that delineate the range of focus when aligned with the aperture that’s being used and the distance from the subject. Jon Sienkiewicz This is a very reliable way of determining DOF. Unfortunately, it is accurate without being precise. The increments are simply too inexact.

As you can see in the image above, this particular scale skips from 1 meter to 1.5 meters to 3 meters to infinity. And you won’t find a scale on a zoom lens since the focal length is literally a moving target. Optical engineers have created DOF charts for many different lenses. Many high quality lenses include these charts in the owner’s manual. DOF can be calculated mathematically using the circle of confusion for a given lens as one of the variables. The term “circle of confusion” describes a spot of light that is slightly out of focus when a lens is focused on a given point. You do not need to know anything about circle of confusion to control DOF. Some digital SLR cameras have a DOF preview button. Even if your camera does have one, don’t trust it 100%. The DOF that your eye perceives when looking through the viewfinder differs from what the camera sees, even when the lens is stopped-down to the shooting aperture. It’s a close approximation, but not identical. Use a DOF chart or the scale described above. Constants Wide angle lenses produce more DOF than telephoto lenses (assuming that film format or sensor size is the same).

Some will argue that if you crop a WA image to match the field-of-view of a telephoto lens the DOF will commensurately diminish. So what? The point remains: put a wideangle lens on your camera and you’ll enjoy more Depth of Field. Depth of Field always extends 1/3 in front of and 2/3s behind the point of focus. No matter whether the DOF is deep or shallow, it always follows this formula. This fact becomes more valuable when you do macro photography. Jon Sienkiewicz Depth of Field decreases as the distance between the subject and film plane decreases. You have VERY little DOF to work with when doing macro photography and are focused just a couple centimeters away, but you have extreme DOF when focused at a point near infinity. All lenses have a Hyperfocal Distance for a given f/stop. If, for example, the Hyperfocal Distance happens to be 16 feet for a particular lens/aperture combination, everything from one-half that distance (8 feet) to infinity appears to be in focus.

If your lens has a DOF scale as described above, line up the infinity symbol with the f/stop you are using and you have just set your lens to its Hyperfocal Distance for that f/stop. Depth of Field sounds like a good thing and usually it is—but not always. If you want to produce dramatic portraits you’ll want to limit DOF, as in the image at the top of this story. By limiting DOF you can make a lens appear sharper. Can you guess why? Depth of Field in Photography Defined: the Basics | B&H Explora Lens focal length Focus distance (distance between lens and subject) DOF is not specific to a certain camera or lens. It is a combination of these four things that creates the DOF we get to observe in a projected image. The first factor is somewhat confusing and intricate. The final three factors are easily controlled by the photographer.

If you feel a wave of confusion bearing down on you and you do not want to reference diagrams, talk about blurry spots, or look at formulas, the following is for you: If you want to take an image with a softer focused background, a shallower DOF, you may use a larger aperture, a longer focal length lens, or get closer to your subject with a given lens. To get an image where the background appears more in focus, a longer DOF, you should narrow your lens’s aperture, use a shorter focal length lens, or get further away from your subject. If your curiosity is heightened and you want to know more about how and why this happens, please keep reading! Then, if you want to know the math behind it, we have you covered in Part II . Circle of Confusion, Simplified Confusingly known as the disk of confusion, blur circle, blur spot, and circle of indistinctness, the circle of confusion (COC) is the most complex and difficult DOF concept to grasp. Here is an illustration of how objects at different distances, although identical in size, will create spots of different sizes (and blur) at the image plane.

The COC is defined as the size of the largest blur spot that still appears as a single point (in focus) in an image. What COC brings to the DOF equation is a standard criterion for sharpness. You may have seen other definitions of DOF that refer to the term: “acceptable sharpness” or “acceptable focus.” By itself, “acceptable” is a subjective term. What might be acceptably sharp or in focus to one viewer might be horribly blurry to another. So, for optics and camera engineers, we need to make this a definitive measurement and not subjective. The term “acceptable” will reappear in this article, but know that, when calculating DOF, “acceptable” is a mathematically defined quantity when discussing sharpness or focus. COC is a function of: Viewing distance Enlargement Visual acuity Viewing distance: The blurry spot above looks like a blurry spot when viewed from a normal distance from your computer or tablet screen. However, if you view this same spot from across a room, it will look like a crisp, clean, green dot. Viewing distance: Let’s get back to that point of light in an image.

If you put your nose to the computer screen, or up to the print or poster, that point of light might look like a blurry spot at very close range. However, if you stand across the room and look at that same spot, it will now look like a single point. If your eye is closer to the reproduced image, the DOF is shallower. Points of light must be points to not look blurry. If you are farther from the image, the DOF is longer. Blurry points might look not-so-blurry from a distance. This animation simulates viewing an object at different distances. Enlargement: The larger the image is reproduced, the shallower the DOF. The smaller the reproduction, the longer the DOF. This factor is similar to the viewing distance described above. Reproduce a blurry spot on a giant highway billboard and it’s a huge, blurry spot. Reproduce it on a tiny wallet-sized print and it might look like a single point of light. Enlargement: An identical image is reproduced at different sizes.

Note how, in the smaller image, the golf ball’s texture is more consistent where, in the larger image, the image shows short depth of field in which only a portion of the dimples are in focus. Visual acuity: We apologize to those with less-than-perfect eyesight. If that point of light looks blurry to you because your eyes are not focusing correctly, your DOF is longer than those who can see the point of light more clearly. The better your vision, the shallower the DOF. Now that we have COC out of the way, the DOF discussion gets much easier to understand moving forward. We are also about to discuss the elements of DOF that we can control directly with our camera and lens. Aperture Aperture , the relative size of the opening of the lens, not only controls how much light enters a lens, it has an effect on DOF. Aperture DOF comparison The larger the aperture, the shallower the DOF. The smaller the aperture, the longer the DOF. Light entering a lens with a diaphragm that has been opened to its maximum aperture will have to be bent more to meet at a single point at the sensor.

Many light rays are passing through the aperture, far from the optical axis of the lens. Because they are bent more, they intersect the image plane at a greater angle than light passing nearer the optical axis. When the light rays converge before or after the image plane—out of focus—the greater angle causes a larger blurry spot to be produced at the image plane and, therefore, produces shallower DOF. Illustration of light passing through a large aperture versus a smaller aperture Light passing through a narrow opening on the lens, a smaller aperture, is passing through the lens much closer to the optical axis and is not refracted as much as light entering at the extreme edges of the lens. This reduction in refraction means that the defocused light rays are closer together when they intersect before or after the image plane—forming a smaller blurry spot at the image plane. Even though the light rays are intersecting before or after the image plane, the smaller angle creates a smaller blurry spot and this gives you a longer DOF. So, to give your photographs longer depth of field, dial in a smaller aperture (larger f-stop number). If you want shallow depth of field, open the aperture (smaller f-stop number).

Focal Length The focal length of the lens, the distance from the rear nodal point of the lens to the image plane when the lens is focused at infinity , has an effect on both your field of view and your DOF. Focal length DOF comparison The shorter the lens focal length, the longer the DOF. The longer the lens focal length, the shallower the DOF. With aperture, we noted that the more refracting of light rays meant a larger blurry spot at the image plane and, therefore a shallower DOF. Here, we have the greater refraction due to the focal length, but, because the lens is a different physical size, we are also changing the distance at which those points are reproduced before and after the focal plane. This change of distance is having an effect on DOF. Why is that? A shorter focal length lens has to bend the light entering the lens at a sharper angle to meet the image plane, because the lens and image plane are closer together. Because of the greater angle of refraction, the out of focus intersections happen closer to the image plane. This shorter distance causes a smaller blurry spot to be created, resulting in longer DOF.

Illustration of light from finite subjects passing through lenses of different focal lengths shows the relative distance of the image points. The farther you move the lens from the image plane—a longer focal length—the less the light needs to bend to intersect at the image plane. This means the out-of-focus intersections will happen at a greater distance from the image plane, meaning a larger blurry spot, thereby causing a shallow DOF. If you want comparatively shallower DOF, use a lens with a longer focal length. A wider-angle lens will give you longer DOF. Focus Distance or Subject-to-Lens Distance The true variable for DOF equations is: focus distance, assuming you have focused on a finite subject. This is the distance from the lens where the focal plane exists. Older lenses had markings on the barrel that told you exactly how far the lens was focused, but many modern lenses have eliminated those markings. Focal plane or subject-to-camera distance DOF comparison Having the focal plane at a short distance from the image plane renders shallow DOF. Conversely, the farther the image plane is from the focal plane, the longer the DOF. This is most easily visualized when you think about some photographs you have likely seen.

A close-up portrait features a background that is not in focus, while a landscape photograph taken across an expansive view will show the foreground river and trees to be in focus, as well as the mountains dozens of miles beyond it. At a greater distance from the subject, light rays will have a narrowed path through the lens and, when the out-of-focus rays intersect before or after the image plane, they will produce a smaller blurry spot and create longer DOF. Illustration of light from finite subjects at different distances passing through lenses shows the relative distance of the image points and the difference in the size of the infinite blur spots. Conversely, place the camera close to your subject and the light rays must be bent more to intersect at or near the image plane. Again, just as with focal length, the change of distance produces a larger blurry circle and, therefore shallower DOF. If you want to have a shallow DOF effect on your image, get closer to your subject. Conversely, move farther away from your subject if you want longer DOF where more of the background will appear in focus. Seeing DOF While You Photograph Let’s finish with: How do I “see” DOF?

Way, way back, when you connected a lens to a camera, the image you saw on the ground glass or viewfinder showed you the light that was making its way through the camera through whatever aperture opening you had dialed in, or at which the lens was fixed. Auto-diaphragm changed this on SLR and other types of cameras. Auto-diaphragm means that when you attached a lens, the camera automatically opened the aperture on the lens to its maximum setting. Why do we want this? If the lens aperture is open fully, you will get the brightest possible image in the viewfinder from which to compose your image. Without auto-diaphragm, what you saw on the ground glass or through the viewfinder showed your depth of field (and sometimes a very dark image). The invention of the “depth of field preview” button allowed photographers with SLR cameras to depress a button and close down the diaphragm to whatever f-stop they had selected. The image would get darker (if you chose an aperture smaller than maximum) and then you could pre-visualize the depth of field for that scene. Release the button and the auto-diaphragm feature would open the lens to its maximum aperture again.

Today, with mirrorless interchangeable-lens cameras and point-and-shoot digital cameras, as well as DSLR cameras with live view, the image you see on your LCD monitor or in the electronic viewfinder will show you the live DOF without having to press a dedicated DOF preview button. Part I Conclusion The bottom line is that, if you know that you can change your DOF by changing aperture, changing your distance from the subject (or focus distance), or by changing the focal length of your lens, and you know how those three things affect your DOF, then you are all set and you can go out and start manipulating DOF while you take photos! Adjusting your DOF changes the way your image looks. Shallow DOF is sometimes used to enhance portraits or close-up macro images, aesthetically. Long DOF is used often by landscape photographers to make sure that both the foreground and the background appear to be in focus. One of the most common questions asked at the photo counter at B&H is, “How can I take portraits with a blurry background?” Utilizing your knowledge of DOF to open up your aperture and close the distance between you and your subject will help you achieve this.

The possibilities of creative DOF are endless, and it all comes down to how you want your image to look, and what DOF your lens is capable of producing on your camera. If you care to dive into the proverbial weeds of DOF, click on Part II to see how mathematics is at the heart of the way DOF is calculated. If you don't give a hoot about the math, and are more into the mythology, proceed directly to Part III . There are a great many articles on DOF online. I sometimes find mistakes in the articles, or conflicting information. What you have read above has been carefully researched and is the best information I feel that I can present. However, if you have a question, comment, or see something that you feel is inaccurate, please bring it to my attention in the Comments section, below. Thanks for reading! Understanding Depth of Field in Photography 50.5 % 49.5 % This exposes a limitation of the traditional DoF concept: it only accounts for the total DoF and not its distribution around the focal plane, even though both may contribute to the perception of sharpness.

Note how a wide angle lens provides a more gradually fading DoF behind the focal plane than in front, which is important for traditional landscape photographs. Longer focal lengths may also appear to have a shallower depth of field because they enlarge the background relative to the foreground (due to their narrower angle of view). This can make an out of focus background look even more out of focus because its blur has become enlarged. However, this is another concept entirely, since depth of field only describes the sharp region of a photo — not the blurred regions. On the other hand, when standing in the same place and focusing on a subject at the same distance, a longer focal length lens will have a shallower depth of field (even though the pictures will frame the subject entirely differently). This is more representative of everyday use, but is an effect due to higher magnification, not focal length. Depth of field also appears shallower for SLR cameras than for compact digital cameras, because SLR cameras require a longer focal length to achieve the same field of view (see the tutorial on digital camera sensor sizes for more on this topic). *Technical Note: We describe depth of field as being virtually constant because there are limiting cases where this does not hold true.

For focal distances resulting in high magnification, or very near the hyperfocal distance , wide angle lenses may provide a greater DoF than telephoto lenses. On the other hand, at high magnification the traditional DoF calculation becomes inaccurate due to another factor: pupil magnification. This reduces the DoF advantage for most wide angle lenses, and increases it for telephoto and macro lenses. At the other limiting case, near the hyperfocal distance, the increase in DoF arises because the wide angle lens has a greater rear DoF, and can thus more easily attain critical sharpness at infinity. CALCULATING DEPTH OF FIELD In order to calculate the depth of field, one needs to first decide on an appropriate value for the maximum allowable circle of confusion. This is based on both the camera type (sensor or film size), and on the viewing distance / print size combination. Needless to say, knowing what this will be ahead of time often isn't straightforward. Try out the depth of field calculator tool to help you find this for your specific situation. DEPTH OF FOCUS & APERTURE VISUALIZATION Another implication of the circle of confusion is the concept of depth of focus (also called the "focus spread").

It differs from depth of field because it describes the distance over which light is focused at the camera's sensor, as opposed to the subject: Diagram depicting depth of focus versus camera aperture. The purple lines comprising the edge of each shaded region represent the extreme angles at which light could potentially enter the aperture. The interior of the purple shaded regions represents all other possible angles. The key concept is this: when an object is in focus, light rays originating from that point converge at a point on the camera's sensor. If the light rays hit the sensor at slightly different locations (arriving at a disc instead of a point), then this object will be rendered as out of focus — and increasingly so depending on how far apart the light rays are. OTHER NOTES Why not just use the smallest aperture (largest number) to achieve the best possible depth of field? Other than the fact that this may require prohibitively long shutter speeds without a camera tripod , too small of an aperture softens the image by creating a larger circle of confusion (or "Airy disk") due to an effect called diffraction — even within the plane of focus. Diffraction quickly becomes more of a limiting factor than depth of field as the aperture gets smaller.

Despite their extreme depth of field, this is also why "pinhole cameras" have limited resolution. For macro photography (high magnification), the depth of field is actually influenced by another factor: pupil magnification. This is equal to one for lenses which are internally symmetric, although for wide angle and telephoto lenses this is greater or less than one, respectively. A greater depth of field is achieved (than would be ordinarily calculated) for a pupil magnification less than one, whereas the pupil magnification does not change the calculation when it is equal to one. The problem is that the pupil magnification is usually not provided by lens manufacturers, and one can only roughly estimate it visually. OTHER WEBSITES & FURTHER READING Norman Koren provides another perspective on depth of field , including many equations for calculating depth of field and the circle of confusion Four Thirds | Four Thirds | Standard Lens Knowledge Lens Technology ●Angle of view and focal length The angle of view represents the subject range that can be imaged with the image sensor, and is expressed in degrees. The shorter the focal length of the lens, the greater the angle of view (i.e.

the lens is wide-angle), and the longer the focal length, the smaller the angle of view (i.e. the lens is telephoto). The angle of view is determined by the lens' focal length and the image sensor's diagonal length, and usually expressed with the following formula. With the Four Thirds system, the diagonal length of the image sensor is about 1/2 that of 35mm film. This facilitates the conversion of the focal length required for a given angle, which is about 1/2 of the focal length of the 35mm film camera lenses. Users who are accustomed to the traditional 35mm film camera can easily estimate the angle of view of a Four Thirds camera (for example, a 14-50mm lens for Four Thirds camera is equivalent to a 28-100mm lens for 35mm film camera). ●F-number F-number represents the brightness of the lens. A bright lens has a low F-number and a darker lens has a higher F-number. The F-number is expressed with the formula shown above.

In general, the advantages of a bright lens include; 1) smooth defocusing; 2) quality imaging at high shutter speeds, in addition to a bright and easy-to-see viewfinder image. ●Depth of field Depth of field is the distance in front of and behind the subject which appears to be in focus. The depth of field in front of the subject is not the same as that behind the subject. Usually, the former is smaller than the latter. The depth of field also increases when the focal length of the lens is short (wide-angle), the shooting distance is long or the lens aperture is stopped down. Therefore, enhancing these factors make it possible to increase the depth of field and attenuating them makes it possible to decrease the depth of field. ●Perspective Perspective refers to the appearance of distance between a nearby subject and faraway subject (the visual effect expressing the distance between them). With a wider-angle lens, the image sizes of nearer subjects increase and the distance of the background is exaggerated. A telephoto lens, on the other hand, compresses distance so the distance between the subject and background is lost.

●Image magnification Magnification is the value representing the size of the image of a subject captured by the image sensor compared to the actual size of the subject. The magnification at which the subject image is largest is referred to as the maximum image magnification. For example, an image sensor that can capture the image of a subject in life size has 1x magnification, while an image sensor that can capture the image only at half size has 0.5x magnification. Image capturing with a high magnification is usually possible with a macro lens, but it is also possible to increase the magnification of an existing lens with a simplified method using an extension tube or teleconverter. (Note) The maximum image magnification of a Four Thirds lens can be converted into the maximum image magnification of a 35mm film camera lens by multiplying "the indicated maximum image magnification x 2". ●Difference between focusing distance and working distance The focusing distance is the length between the focused position of the subject and the image sensor, and the working distance is the length between the focused position of the subject and the front of the lens.

This means that, when the focusing distance is identical, the working distance is smaller when a lens with a larger overall length is used. ●MTF The MTF (Modulation Transfer Function) curve is a lens performance indicator that represents how faithfully a lens can reproduce the contrast of the subject. The MTF curve is drawn by taking the contrast reproduction rate (%) on the vertical axis and the distance from the image center (mm) on the horizontal axis. Evaluation is performed with a set of two curves, including the S (Sagittal) curve in the radial direction and the M (Meridional) cover in the concentric circle direction. The MTF curve chart shown here shows how the contrasts of an image containing 20 sine waves per mm and an image containing 60 sine waves per mm can be reproduced. In general, the curve for lower frequency approaches 100% when the lens has a high contrast, and that for higher frequency is high when the lens has high resolution. The frequencies used for this evaluation vary depending on the design policies of manufacturers.

Basic Photo Tips: Depth of Field - photo.net Basic Photo Tips A Site for Photographers by Photographers Search Home > Learn About Photography > Basic Photo Tips: Depth of Field Featured Equipment Deals Tweet There are certain photographic truths that apply to all cameras, regardless of whether they’re DSLRs or compact point-and-shoots. Depth of field is one of those truths. It’s a photographic term used to describe the area of an image—from near to far (or, in front of and behind your subject)—that looks sharp. Let’s say you’re taking a picture of a friend standing outside surrounded by trees and shrubbery. Naturally, you’re going to focus your lens on your friend. Everything that’s on the same plane (also known as the plane of critical focus), i.e., objects that are the same distance from the lens as your friend, will also be in focus. If you increase the depth of field, some of the trees and bushes behind and in front of your friend will also look sharp. Before we go into details about how and when to change your depth of field, let’s talk a little about sharpness and the human eye.

Notice that earlier we didn’t say that the objects falling within the depth of field range were in focus, but rather that they looked sharp. There’s a difference. To put it simply, a lens can only focus on one distance at a time since the sensor (like a strip of film) is a flat surface. So, if your subject is eight feet from the lens, other objects that are also eight feet from your lens (along the plane of critical focus) will be in focus. The objects in front of and behind the subject will not be as sharply focused as those that are perfectly parallel to the sensor at the same distance. And, in fact, the sharpness of objects will get softer the farther away they are from the in-focus subject. However, depending on the image and its depth of field, our eyes may not be able to discern the differences in sharpness. The apparent sharpness of an image, in part, depends on image size and the viewing distance from the image. If you stand close to a large print, for example, you will notice the softer focus areas more readily than if you were standing farther way from the print or if the print were smaller.

Shallow depth of field It Starts with the F-Stop When it comes to depth of field, the most important tool you have is the f-stop, or aperture setting. The size of the aperture controls how much light enters the camera. In turn, the aperture affects how much of the image appears sharp. A higher number, like f/8 or f/16, means the camera will use a smaller aperture opening and, therefore, deliver a broader depth of field, with more of the image appearing in focus. A lower number, like f/2, gives you a larger aperture opening and a shallower depth of field, softening the background (which creates an often-desired effect called bokeh ). In order to manually adjust f-stops to affect depth of field, your digital camera needs to have an aperture priority or manual exposure mode. In aperture priority mode, you choose the aperture and the camera chooses the shutter speed (in manual mode, you choose both). Keep in mind that, unlike DSLRs with a full range of aperture settings, some compact cameras have a limited range of f-stops, often topping out at f/8 or, at the higher end, f/16.

No worries, both are sufficient to give you increased depth of field. Assuming you want an increased depth of field, with more of the image appearing sharp, set your camera on aperture priority and stop down the aperture (set the aperture to a higher number). At the same time, be sure to check the shutter speed the camera has chosen. If it’s too slow to hand hold, either use a tripod to steady the camera or open up the aperture until the shutter speed is faster. Choosing Between Broad and Shallow Depths of Field So, when should you use a broader depth of field? Any time you want all or most of the components of your photograph to appear sharp. Landscapes, a field of flowers, the interior of a room, and a group of people are all good candidates for increased depth of field. That’s a broad range of subjects and one might think that all photographs will benefit from an increased depth of field. Not true. Decreasing depth of field can result in a more powerful image, depending on the subject matter and the feeling or message you want to convey. Portraits are the perfect example of when to use a shallow depth of field.

By allowing the background to soften or blur while your subject is sharply focused, it puts the emphasis on the person rather than on his or her surroundings. A field of flowers may look wonderful when the entire flora fall within the camera’s depth of field. But perhaps you particularly like a small group of those flowers or even an individual blossom. If you have a shallow depth of field, the eye will be drawn to those few choice plants or single flower. Shallow depth of field Or, let’s say you’re photographing several people, but you want one of them to be the main subject matter. With a shallow depth of field you can focus on that one person—giving him or her more importance in the photograph—and let the others fall out of focus. Again, keep in mind that the farther away those subjects are from the main point of focus, the more out of focus they will appear. Broad depth of field The Long and Short of It Most digital cameras have zoom lenses, allowing you to shoot at different focal lengths. These different focal lengths also impact how much depth of field you get in a picture. The rule of thumb is that the shorter the focal length, the broader the depth of field.

Conversely, the longer the focal length, the shallower the apparent depth of field. Check it out for yourself. Standing in place, set your lens to its widest focal length and take a photograph. Then take the same picture, from the same distance, zooming in to the lens’ longest focal length. More of your picture will appear sharp when you shoot in wide angle. Along the same lines, the distance from camera to subject affects depth of field. Using a “normal” focal length (try somewhere in the middle between wide angle and telephoto), take a photograph while standing a few feet from your subject. Then, keeping the zoom at the same “normal” setting, step back about 8-10 feet and take the same photograph. The depth of field should be greater in the picture when there was more distance between your lens and the subject, so more of the image will appear in focus. Think about how you take pictures. When you shoot a landscape, chances are you shoot at wide angle. Not only does a wide angle give you a broader angle of view, but it allows you to capture a larger area with more of the image in focus.

Broad depth of field Longer focal lengths, like moderate telephoto, are usually used in portraiture for several reasons, one of them being depth of field. When taking portraits, like headshots, your main subject matter is the person’s face and shoulders. Unless you’re shooting in a studio, with a complementary background, chances are you don’t want any distractions in the background or foreground. If you shoot with a telephoto lens (long focal length) and focus your lens on the person, the area surrounding your subject will be softer and, therefore, less of a distraction. The best way to see how depth of field affects your images is to experiment. Try working with different f-stops, focal lengths, distances between lens and subject, and various combinations of the three. Be sure to take a notepad and pencil with you so you can keep track of your research. Making great images is about control and consistency. Each time you learn to control another aspect of your picture taking, the more likely you are to make great images time after time.

Tutorial - lens micro adjustment Tutorial - Lens Micro adjustment Background The later generation cameras from Canon and Nikon (and some others) have the facility to fine-tune the autofocus of their lenses to the camera, to remember the adjustments necessary and apply them when that lens is attached again. Cameras are smart as they recognise and report which lens has been put onto them and automatically apply any adjustment that you dialled in previously. They can even detect the presence of a teleconverter and remember these settings too. Before lens micro-adjustment, if your lens wasn't quite calibrated accurately to your camera, you had no choice but to send it back to the manufacturer for calibration. Now you can do it yourself provided the errors are not way off spec. So what are we talking about here exactly ? Well, if the lens and camera's autofocus are precisely matched to each other then the camera will focus accurately on the subject, but if the point of focus wrongly falls just in front of the subject, then camera is said to be "front focusing" and if it falls just behind the subject it is said to be "back focusing". These focusing errors may not be immediately obvious but will make your images look soft and you will not be getting the best out of your equipment.

So how come the manufacturers are selling equipment that front or back focuses ? Well, if you consider that pretty well all manufactured goods are produced to a tolerance range, it is possible to be unlucky and pair a camera at the positive limit of its acceptable manufacturing tolerance range with a lens that is also at the positive limit of its acceptable tolerance range and have a combination that is way out of spec. To clarify this point let's imagine that both cameras and lenses have a manufacturing tolerance of zero plus or minus 5 arbitrary units. Now let's say that the camera we buy turns out to be +5. It is still in spec (just) and will be released for sale. If we pair this with a lens which has a value of -5 then the errors will effectively cancel each other out as the overall value will be zero and the pairing will focus beautifully despite both being at the tolerance limit extremes. However, if you paired a +5 camera with a +5 lens then then resultant +10 would cause focusing errors that are sufficient to produce soft images. Lens micro adjustment enables us to dail-out these errors in camera. Which cameras can be micro adjusted ? In the Canon range that I am most familiar with, the following cameras with Liveview have this ability.

Certainly those cameras from the EOS 50D, 7D, 5DII, 1DmkIII and 1DSmkIII and presumably all models onwards will have the facility. In the Nikon ranges I believe that the D300 onwards, D700 and the D3/D3x onwards have this facility. The Sony A900 and the Pentax K20 also have this facility. If your camera predates the ones listed above then you will not be able to adjust your lenses, but you should still check for front or back focusing. If you have evidence that you have a bad combination then the only solution is to send the lens and camera back to the manufacturer for calibration. How do you set the lens micro adjustments into the camera ? Whichever method you use, you will need to set the adjustments into the camera for each lens using the appropriate custom function. Below is how you do it with a Canon 1DmkIV, just check the handbook to find it on your camera. For example, on a 5DmkII it is CFn III-8, on a 1DmkIV it is III- 7 and on 7D it is III-5.

Select Autofocus /Drive in the appropriate custom function Select Adjust by lens Press Info to change the value (if you have trouble here you probably pressed Set instead of Info) Dial in the forward adjustment (-) i.e. toward the camera or backward adjustment (+) i.e. away from the camera that you determine from one of the methods described below) Press the Set button to accept the value. Every one of my Canon lenses on every camera I have used has required either zero or (+) adjustment, none of them have required (-) adjustment. Set CFn to adjust by lens and press Info to change Micro adjust screen. This lens front focused and required a value of +9 to correct it What methods are available for lens micro-adjustments ? These range from expensive ready made focusing kits that you can purchase to DIY versions using sloping focusing charts or focusing on interference patterns on a computer. These are all covered below but my favourite method using a tethered laptop described at the end of this tutorial. I have tried all of these methods but by far the best one in terms of speed and accuracy is the "tethered" method described at the very end of this tutorial.

However, this method only relevant to one of the latest generation cameras that are capable of autofocusing whilst in liveview. If you are lucky enough to have one of these and have access to a laptop computer, skip to the tethered technique instructions below. I know it sounds a bit scary, but trust me on this - it is really easy and uses the Canon software provided with your camera to run it. I should add that none of the methods described here are recommended by Canon other than their own one - but don't let this deter you! Quick check using the latest cameras This is a quick check or temporary method if you are short on time. It capitalises on the fact that the latest cameras have such high resolution rear screens that you can zoom in and check critical focus without resorting to looking at your images on a computer. Once you have determined whether you have 1) front or back focusing and 2) the approximate value you can fine tune around more thoroughly later. With the camera mounted on a tripod you can focus on a fixed target (a banknote taped to a window is fine) and then switch the lens carefully to manual focus.

Zoom in to 10x using the + magnifying button on the back of the camera and see if you can improve on the camera autofocus by focusing yourself manually. If you can better what the camera can do yourself you need to dial in a bit of lens micro adjustment as described in the other methods here and then recheck it. When I first got my Canon 24-105 lens I thought that the images from it looked a little soft, so after doing a 5 minute check and adjust I ended up with quite a large +10 adjustment that made a big difference to sharpness. When I had time to set the lens up accurately using the tethered method I found that I needed +9 so I was not far out. Canon's method * Mount the camera on a good tripod. * Set up a target for the camera to focus on. The reference target should have sufficient contrast for the AF system to detect. It should be flat and parallel to the camera's focal plane, and centred. * Lighting should be bright / even. * Camera-to-subject distance should be no less than 50 times the focal length of the lens.

For a 50mm lens, that would be at least 2.5 meters. * Set the lens for AF and the camera for One-Shot AF, and manually select the centre focusing point. * Shoot at the maximum aperture of the lens via manual mode or aperture-priority. Adjust exposure level to get an accurate exposure. Use low ISO setting. * If the lens has an image stabilizer, turn it off. * Use a remote switch or the camera's self-timer to fire the shutter. Use mirror lock up as well. * Take three sets of images at microadjustment settings of -5, 0 and +5, i.e, three consecutive images at -5, three consecutive images at 0, and three consecutive images at +5. * Look at the images on your screen at 100% magnification. * Take additional sets of test images at different microadjustment settings if necessary until the sharpest image is achieved. * Register the corresponding microadjustment settings in the camera. Notes from Canon For best results, manually set the focus on the lens to infinity for every exposure before allowing the camera to autofocus the reference target.

Expect some minor variations in focusing accuracy within each set of three test images, even though they were all taken at the same microadjustment setting. This is completely normal, and is due to the tolerances of the camera's AF system. Expect smaller microadjustment settings to have a greater effect with telephoto lenses, and vice versa for wide-angle lenses. If you are attempting to set microadjustments for a zoom lens, it is important to realize that the camera's setting may only be accurate for the focal length setting you test. The instruction book suggests testing at the longest focal length of the lens, but you may find it more efficient to choose the focal length you use most often. Sloping chart method Both this and the Canon method can be used to check the focus on a camera that lacks lens micro adjustment but you will just not be able to make any adjustments of course. If you find significant errors you might need to send the camera and/or lens back to the manufacturer for calibration. The method follows Canon's recommendations above other than it uses a sloping target. You focus on a thick black focusing line and look to see if the text is equally in focus in front and behind the focusing line.

I use a target that you can download from Tim Jackson's website here: Tim Jackson lens adjustment chart . I glued it using spray mount to a flat board that I propped up at a 45 degree angle with a triangular piece of wood (also glued to the board using wood glue). Front focus requiring (+) adjustment Back focus requiring (-) adjustment The benefit over the flat target is that you are able to see straight away which way (front or back) to adjust the camera whereas the flat target just tells you it is out of focus. The minus is that it is less accurate as it depends on the camera and chart being aligned very well in every plane. Some of the commercial products use this method but have a means of accurately aligning the camera. However, I have used the home made chart for some time, just aligning it by eye - with considerable success. Adjustment is best carried out when the light is not constantly changing and is good but not too bright. I often do this indoors on a dull day indoors using a desklamp as the light source. You may have to override your camera's meter as the chart is white and will fool the metering into under-exposing.

The lens under test is mounted on the camera/tripod and using a cable release, set the camera to One shot in Av mode. Focus at the lens's widest aperture to minimise depth of field on the black line at the centre of the test chart. I usually place the tripod at a distance from the target that seems relevant to the lens focal length, that is, where I can read the chart numbers and determine if they are in or out of focus. Canon recommends using a vertical target and testing at 50x the lens focal length. I find that this is often a bit excessive. If you were testing a 600mm lens at 50x 600mm that means 30 metres - at which you would need a very big target. I do all my testing at the kind of distance I usually shoot at which is much closer and seems to work well for me. For a 100mm macro lens, the recommendation is 50x100 i.e. 5 metres. I would test a macro lens at about 1 metre.For zoom lenses Canon recommends setting the zoom to the maximum focal length or alternatively to the focal length you use most and that is what I do.

Next you need to roughly know whether the camera is front or back focusing so take a quick series of photos at various plus and minus micro adjustment settings, then view them on the back of the camera. If you have one of the later high-res screens you can determine whether the camera appears to be front or back focusing. If the screen is not of sufficiently high resolution to tell this then you will need to view them on a computer screen before you can go any further. Next, if you think that the camera is front focusing for example, take a series of images in triplicate from zero backwards and then view them on the computer screen at 100%. From this you can determine which settings are required to make the focusing error zero. The appropriate camera lens micro adjustment value is then dialled into the camera and rechecked so that the numbers in front and behind the focus line on the chart are equally in focus. It is all done by trial and error and is admittedly a bit time consuming ! Interference pattern (Moire fringe technique) This method is much the same as those above but uses a novel target viewed on a laptop screen- so is best viewed indoors. It utilises a clever test pattern that was developed by by Bart Van der Wolf .

It is not a printable target - you must use a computer screen to view it.You are striving to achieve "maximum interference" at which point lots of circular patterns appear on the laptop screen and you will see colour fringing which looks a bit like oil on water. At this point the lens is extremely accurately focused. Tethered technique for later cameras that can autofocus in Liveview Finally I get to my favourite method, and the one that I currently use. It was first described by Arash Hazeghi on the Birdphotographers.net website and is quite ingenious. It is only relevant to cameras that can autofocus in Liveview. This includes: Canon cameras: 50D, 1DmkIV, 5DmkII, 50D and 7D and may be possible on some others too. Presumably later cameras will also have this function. In the Nikon range, D300, D300S, D700, D3, D3s and D3x are all apparently OK. You will need a computer loaded with the Canon EOS Utilities software that came with your camera. If you shoot Nikon you will need to have purchased and loaded Nikon camera control Pro2 software.

A laptop is most practical as you are not restricted to working off your desk with it. I use a banknote as the target taped to an angle bracket from a hardware store, alternatively you could stick it to any vertical surface with masking tape. A banknote has lots of very fine engraved detail on it which is excellent for checking focus. My usual target - a banknote taped to an angle bracket with masking tape There follows Arash Hazeghi's method. He describes using a mirror to check alignment but I must admit I skip this step for speed and have not found this to be necessary if I set everything up reasonably by eye. Arash Hazeghi's method (my notes in red) "Pin the target to the wall at a distance ~25-50 times the focal length, for a zoom lens choose the focal length that you use most often. First use the spirit level on the ball head to level the camera in XY plane. It is essential that sensor plane is parallel to target. To do this you can use a small mirror, tape it to the target look through the camera’s finder until you can see the centre of your lens in the mirror and lock down your tripod.

Optical axis is now perpendicular to target and you are done with the mirror. I skip this step, just setting up quickly by eye. You must have Canon EOS utility application installed on your machine, this is included with every Canon camera, if you have an older version make sure to go to Canon’s website and download the latest update. You are ready for micro adjust now. Follow these steps: First set the camera to Av mode and select the centre AF point. Dial in any necessary exposure compensation to get the exposure correct on your target. 1) Connect the camera to your computer via the USB cable that came with the camera and cancel any image download pop-up/application 2) Run EOS utility. 3) Click on Camera setting/remote shooting icon The camera should now magically switch into liveview 4) Click on Remote Live View Shooting. This will open a new window with live sensor video feed 5) Make sure AF is in phase detect mode (Quick mode AF) that uses the camera’s main AF sensor. This is found within the Liveview menu 6) Choose the centre AF point and make sure the white rectangle is centred on the AF point 7) Click on the magnifying icon for a full size view .

8) Click AFON button the camera will now perform AF. If you have assigned any function to the camera AF ON button within the custom functions then you will need to reset it temporarily back to the default or the camera might not focus! 9) Click on 200% magnification, you are now viewing the sensor output at 2:1). Note it is essential that the tripod be placed on a solid surface plus nobody should walk in the proximity of the setup or you will see vibrations on the screen! 10) Now click on the ( > ) or( < ) buttons to shift focus back or front one click at a time until image appears sharpest on the screen, notice the contrast edges, you want them as crisp as possible. Write down how many clicks you have moved relative to the centre, infinity symbol indicates far direction 11) Repeat this a few times until results are consistent. It is best to defocus the lens and get the camera to refocus within EOS Utility a few times to check for consistency. 12) Each click on the ( > ) or ( < ) corresponds to one unit in the AF micro adjust scale in the camera. e.g.

if you clicked the > icon 3 times in the + direction then dial in +3 into the camera Lens microadjustments 13) Disengage LV by clicking "close" in the Zoom View and Remote Live View Windows. 14) Go to MA menu option in your camera and dial in the exact value noting the back or front direction. 15) Go back to step 3 and perform AF again, if the image is already as sharp as possible when you click 200% you are done, if not iterate until you can repeatedly get the sharpest image. Your camera and lens static AF should be adjusted with great accuracy now. " Depth of Field - Digital Photography Tutorial - Photoxels Depth of Field What is depth of field, what affects depth of field, and how can we use an understanding of depth of field to take better pictures? This One Pager Tutorial will make everything clear from near to far. What Is Depth of Field (DOF)? Depth of field (DOF) is the distance wherein objects are in focus. This is the pragmatic explanation. To be technically correct, DOF is the zone of acceptable sharpness, the area in front of, and behind, a focused subject that appears in focus.

Circle of Confusion (COF) Technically, only the subject in focus -- and all other objects at the same distance -- are in focus; everything else in front and behind are out of focus. How much out of focus depends on a term called the "Circle of Confusion (COF, or COC)." Let's see if we can make that term clear, but if you don't understand it, don't worry. Many photographers take superb pictures using depth of field to their advantage never having heard of COF. I never did until I started researching this topic. And, I find that it just confuses the hell out of most people, so if you want to skip to the next paragraph, here is your chance to do so . OK, back to the COF. Imagine we are photographing three (3) dots. They are the tiniest dots the human eye can clearly make out, and of course, we are assuming perfect 20-20 vision and ideal light condition.

So, here we have these 3 dots, arranged one behind the other (with the closest dot to the right of the middle dot, and the farthest dot to the left of the middle dot, so a camera can take a picture of all 3 dots). Now, we focus our lens on the middle dot, which comes out in perfect focus. The two other dots also appear in focus, but peering closely at the resultant photograph, we notice, however, that the dot in front of and behind the middle dot appears as circles instead of perfect dots. I.e., technically, they are out of focus, but to our naked eyes (at a "normal" distance), they "appear" in focus. It is this circle that we call the "Circle of Confusion." So the COF is the diameter of a dot such that when we view it with the naked eye, it appears in focus. If this circle gets past this diameter, our eyes tell us it's out of focus. Lens manufacturers have to decide what that diameter is going to be and design their lenses accordingly to be able to resolve a dot within that COF so that it appears sharp to us.

For a more technically detailed explanation of how COF is determined by lens manufacturers, read Michael Reichmann's excellent tutorial: Understanding Depth of Field . That is about all I am going to say on COF. Do you need to understand COF to use DOF? Personally, I don't think so. But if you are one of the people who absolutely must understand COF, its history, how lens manufacturers calculate DOF based on the COF, etc. etc., just check out the link above or do a search on Google. There's enough material there to keep a technical mind happy for many hours. What Affects DOF What we really want to know as photographers is what affects DOF so we can control DOF in our pictures. For a long, long time, photographers have gone with the following three criteria: lens aperture distance from subject focal length While the first two are technically correct, the third one has raised somewhat of a storm of controversy among certain circles. Why exactly, we will make clear later. Let's look at each of the three criteria in more detail. Lens Aperture The aperture is simply the size of the opening that allows light to go through the lens.

It is expressed in f/stops (also referred to as f/value or aperture value), and a typical aperture range is f/2.8 - f/8, giving the range from maximum (large at f/2.8) to minimum (small at f/8) aperture. A small f/value (e.g. f/2.8) indicates a large aperture. A large f/value (e.g. f/8) indicates a small aperture. So, f/2.8 is a larger aperture than f/8. Generally, a large aperture gives a shallow DOF, and a small aperture gives great DOF. f/2.8 +0.7EV, Macro, Tripod used Minolta DiMAGE A2 In most consumer digital cameras, you may not be able to directly control the aperture. Many, however, provide a Portrait scene mode and a Landscape scene mode that basically do what we are after, i.e. use a large and small aperture, respectively. As most of you have found out by now, it is quite difficult to obtain a shallow depth of field with most consumer digital cameras even with the aperture opened up wide. Why? See the section on focal length below.

Distance From Subject When you focus on a subject close to the camera, the DOF is less than when you focus on the subject farther away from the camera. Putting Distance From Subject into practice: Step away from your subject to obtain greater DOF, or move in closer to decrease DOF. Moving In Close: Even though we use a small focal length (35mm, 35mm equivalent) and a small aperture (f/7), by moving in close (macro), we are able to isolate the subject from the background. If we had used a larger aperture, we would have obtained even shallower DOF. Fujifilm FinePix S7000 Focal Length Set your subject in front (say, about 3m or more) of a bush (or a tree with lots of leaves, or some other kind of busy background). Use wide-angle and take a picture. Both your subject and the bush would most probably be in sharp focus. The background may distract from your main subject -- unless you're aiming for a Product Shot where you want to situate your subject in his or her environment, and do want both subject and background to be in sharp focus.

Now zoom in and fill in the screen with your subject's face and shoulders. Look at the resulting image and you'll probably notice that, though your subject is still in focus, the bush now appears out of focus, giving a nice blurred background that does not steal attention from your subject. Photographers use this technique very effectively to "affect" DOF. So, a wide-angle lens has greater DOF than a telephoto lens. Most consumer digital cameras have very short focal lengths and that is why it is so difficult to obtain shallow DOF, even with the aperture opened up wide. I promised to come back to the storm of controversy brewing in some circles that disputes that focal length has any effect on DOF. The contention is that, for a fixed image size in your screen, the DOF is unchanged irrespective of focal length used. And they have pictures to prove it ! However, photography is part technics and part art. The technics part may well tell us that DOF is the same at all focal lengths for a fixed image size on screen. What this is saying is that we achieve the same DOF whether we fill the screen with the face by walking to the subject, or backing off and zooming in.

The art side, however, tells us that a long lens (i.e. long focal length) reduces the distance from the subject and thus provides a shallow DOF. Yes, we can achieve the same narrow DOF by walking close to the subject. However, the results look very different! Why? Because a long lens also provides a "flattened" perspective which makes the narrow depth of field much more prominent than walking closer to the subject using a lens with normal focal length does. The link above with all the pictures prove it. Putting Focal Length into practice: Use long focal lengths to achieve the effect of a shallow DOF.

Long Focal Length: Bu using a long focal length (380mm, 35mm equivalent), we are able to "throw the background nicely out of focus" Minolta DiMAGE Z1 Putting It All Together Putting it all into practice: A large aperture (f/3.2), moving in close to your subject (macro) and using a long focal length (112mm, 35mm equivalent) has thrown the grass into a nice green blur Olympus Camedia C-8080 Wide Zoom A Word On Aperture Following our rule of thumb on using a small aperture to obtain a great DOF, does this mean that we should always use the minimum aperture if we want the greatest DOF? It sounds logical, but because of diffraction that comes into play when the aperture is too small, this may affect the quality of the image, giving the appearance that some objects (especially light sources) are not in focus (but hey, use this to your advantage to obtain starry effects when photographing light sources!). So you don't have to stop down to the smallest aperture for maximum DOF.

For example, on 35mm cameras (where the aperture stops all the way down to f/11 or even f/16), f/5.6-f/8 are usually the best apertures to use for maximum DOF. On digital cameras, try f/5.6. Pseudo DOF A word of caution. Some use post-processing and apply a Gaussian (or other type of) Blur to achieve a blurred background effect. Depending on your skills, this may be quite effective but, to a trained eye, this is almost always apparent and looks "false." So never try to pawn off a processed blur as naturally obtained shallow DOF. Also, be careful not to apply this blur effect to all your pictures, but only to a few whose subject matter will benefit from it and where it won't matter that the blur is processed, not natural. Summary Even though the subject you focus on is the only thing technically in focus, some objects in front and behind your focused subject also appear to our eyes to be acceptably in focus (thanks to the COF). This zone of acceptable sharpness is the DOF.

We can increase the DOF (or the appearance of it) by using a small aperture, moving away from our subject, or using a wide-angle lens. We can decrease the DOF (or the appearance of it) by using a large aperture, moving closer to our subject, or using a long focal length. Our Readers Write Back

Question: In film and photography, what is the name for the distance in front of and behind the subject which appears to be in focus?
Answer: Depth of field