Recommendations for new video camera for my channel  - Page 1
Forum section: electronics / general

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 05:19:12 am
content: Hi all,Anyone that follows my channel knows I have been trying to improve my video setup over the past few months.I purchased a Canon EOS750D DSLR camera and have been recording with that for the past 5 months or so, but I have been struggling with the focus range. As I use an over bench view the camera has to focus for about half of the distance. I have tried setting the f to a larger number to do this, but a side effect is that it greatly reduces the sharpness overall and the resulting high ISO setting results in graininess, FYI I currently have about 3000 Lumen of light at the bench top, with 95CRI lights.Prior to spending $1000 on this camera I was using my iPhone 6S to record the footage, it could do a better job in most cases, but the lack of optical zoom was a pain.So I am now seriously thinking of buying another camera, this time a 4K video camera (I only intend to do 1080p but figure that a better camera will have more headroom quality wise).The main criteria for me is that it must allow for a wide focus range with good video quality, so it can focus from about 20cm to about 1m away at the same time, it must also have a flip out and rotating screen so it can be seen from the front when needed, and external mic input.Anyone have any suggestions, or advice ?

author: EEVblog
author_rank: Unknown
timestamp: August 30, 2018, 05:37:27 am
content: Are you actually talking about depth of field?i.e. havingeverythingin focus at the same time over that distance?Or just theabilityto focus over that range.I suspect you mean the former, but it's not clear.I mostly leave my camera set at a fixed F5.6 as a tradeoff for greater depth of field vs potential image degradation (grain noise) due to lack of light. It was a lower value on my previous camera.My new cam is the Sony NX80, and has been very impressive, but not cheap.

author: EEVblog
author_rank: Unknown
timestamp: August 30, 2018, 05:41:33 am
content: Oh, I see you said at the same time, so you mean depth of field.Having an overhead bench cam you can see and use (below head height) and then asking it to get half that distance depth of field focus at that distance is an incredibly tough ask.i.e. asking a camera to have depth of field of say 25cm from 50cm away is a tall order.I suspect to do that properly you'd need a full frame camera sensor perhaps if your previous APS-C sized sensor couldn't do it. Either that, or a faster lens.Personally I'd look at arranging your setup so you don't need such a large depth of field.A 4K camera for the same sensor size and lens speed is actually going to give you worse performance as the light gathering of each pixel is smaller.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 06:29:21 am
content: Thanks Dave, yes I meant depth of field, at least one of us knows what I’m talking about, pity it’s not me lol.I did have the camera lower and as you mentioned having it further away helped a bit, it currently sits at head height whilst standing.The setting I found that seems ALMOST good enough is f16, anything lower than that results in very obvious out of focus whilst moving on the bench, but higher results in a sudden drop in quality, even 16 is pushing it with the quality.Unfortunately my work space is very small, I don’t really have room for a tripod in front of me whilst working at the bench, as you do, the above bench view is what works best for me, usually, even if I would prefer to do it differently!I don’t want to take another expensive gamble on a camera, the DSLR hasn’t been completely suitable for this, but it has at least taught me a bit of what I do actually need!

author: rjp
author_rank: Regular Contributor
timestamp: August 30, 2018, 06:34:59 am
content: smaller sensors and wider/shorter lenses give you more DOFlarger sensors and bigger lenses give you less.you can muck around with all this at places likehttp://www.dofmaster.com/dofjs.htmlif you want to see whats possible with your camera.I would have *thought* a < 30mm lens on your camera would get you in the ballpark.

author: boffin
author_rank: Unknown
timestamp: August 30, 2018, 06:50:39 am
content: I'm currently using a canon HF600 on a Monopod which is stick into the wall. I have two (cheap) swivel mounts back to back on the end of the monopod, so can aim the camera in pretty much any direction/angle. For closeup shots I use my celphone (Samsung S8) held on a celphone mount at about 10cm and the zoom on the phone. Cheap, or what I had on handOh, and a MAONO Lavalier Microphone, $25 from Amazon. Possibly the best investment I've made

author: EEVblog
author_rank: Unknown
timestamp: August 30, 2018, 07:24:43 am
content: Quote from: TheDefpom on August 30, 2018, 06:29:21 amYep, running F16 is nuts, you need a seriously fast lens and a metric crap ton of light.QuoteFlexible arm mounted on the bench edge?https://www.digitalcamerawarehouse.com.au/manfrotto-237hd-heavy-duty-flexible-armI have one of these on my edited bench video camera.QuoteMaybe consider a better lens?

author: tautech
author_rank: Super Contributor
timestamp: August 30, 2018, 07:28:01 am
content: Since you got the new cam Scott your focus (excuse pun) has been on improving lighting and this has definitely helped and in general pic quality is pretty good however lately the auto-focusing is noticeable and could be improved some by just happening faster as Dave mentioned.If we look your HDMI tester fix vid, the closeup work looks fine but the bench work could do with more lighting still.Yep you have been cursing it for a while but results are improving so maybe just some more tweaks will get you the results you seek.

author: EEVblog
author_rank: Unknown
timestamp: August 30, 2018, 07:48:09 am
content: Quote from: tautech on August 30, 2018, 07:28:01 amSeems to be some form of spot light on the bench? An improved lighting solution could do wonders here.Also, the audio background hiss is quite noticeable, certainly something that can/should be improved.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 07:49:09 am
content: Rob that video had about 1800 Lumen, I have since added another light and got it physically wider to give more even lighting, and as I said its now about 3000 Lumen, if I crank the lights right up I can just get 4100 Lumen, aka a crap ton, but I don’t like to run things maxed out, they last longer that way.Ok so maybe a different auto focus lens is the way to go, this one is very slow so I (when I don’t forget) set manual focus instead, if the auto focus was fast I could probably use that and avoid the issue, but certainly being able to set a big depth of field will go a long way if I can get that right.From memory I think the one it came with is 18mm-55mm or something like that.I will look at that link Dave and see if it is something I could use, I tend to swing my arms around like a chimpanzee so anything in the way has to be able to take a hit lol.

author: tautech
author_rank: Super Contributor
timestamp: August 30, 2018, 08:00:21 am
content: Quote from: TheDefpom on August 30, 2018, 07:49:09 amYeah that wasn't the best example of your latest work where the auto-focus has been more noticeable.This your latest @~45s shows clearly the auto-focus issue:https://youtu.be/vodPQq25vM4?t=40

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 08:04:43 am
content: Dave, I hadn’t actually noticed the hiss, but now you pointed it out I can hear it, yes it is pretty loud.I might have to add some filtering to the audio to cut that out, I tend to boost the audio by about 3dB maybe 6dB depending upon if I am standing or sitting, I try to aim for a level around -6dB in the final audio if I can.I tried a few different mics and using the built in one seemed fine compared to the ones I tried,better in some cases, I do use automatic level control in the camera though, that might be part of the issue.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 08:11:06 am
content: Quote from: tautech on August 30, 2018, 08:00:21 amThat section of the video was recorded about 5 months ago whilst I was still living in the garage after the flood. It is actually from a Logitec C922 webcam, at the time I was looking at different production methods and I experimented using OBS with the webcams to record, I had issues with some bugs in OBS (I actually lost a bunch of footage because it only recorded at 1 FPS randomly!).It was actually these issues that prompted me to buy the Canon DSLR.

author: tautech
author_rank: Super Contributor
timestamp: August 30, 2018, 08:14:46 am
content: OK Scott then are only the recent post bags displaying your current setup......oh and the SPD1168X vid ?

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 08:17:10 am
content: Yep that would be about right.I have so much footage shot for various videos which I am yet to publish, sometimes it even stretches back to last year before the flood!

author: EEVblog
author_rank: Unknown
timestamp: August 30, 2018, 08:57:28 am
content: Quote from: TheDefpom on August 30, 2018, 08:04:43 amYep, auto again control almost never works, I never used to use it until I got the Sony NX80 which works superbly, but it's got a proper mic pre-amp and I'm using studio quality external rode condenser mics.Can't you get a good quality lapel mic?If you have an external mic input then there are countless options available.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 09:16:43 am
content: When I was recording on my iPhone I used a lapel mic on a boom arm, that mic is a trrs, so it won’t work on the Canon which has a standard 3.5mm trs, I might have to try and find something.I think solving the video quality issue is the priority though, changing the camera might solve both at once... am looking at about NZ$1700 if I do go with a 4K, but if I will get better results by sticking with 1080p then at least it will be a bit cheaper, this yt thing gets expensive!

author: wilfred
author_rank: Super Contributor
timestamp: August 30, 2018, 10:48:25 am
content: I'd start with brighter lights and stop down and set focus manually. Take control and take care. I really don't think you can spend your way out from under the laws of optics.Depth of field is a function of lens focal length, Aperture and subject distance. Also included is something called the circle of confusion, an arbitrary point at which the out of focus image is determined to be acceptably sharp under normal viewing conditions. You can't control this so you can ignore it.The aperture number is the focal length divided by the physical diameter of the diaphram.Your iPhone was acceptable because it has a short focal length lens and this is squared in the equations so it has the biggest influence in any given setup. It sounds to me like your ideal camera will be one with a short focal length lens.Cinematographers generally favor a DSLR because the larger image sensor allows use of longer focal length lenses for a given angle of view and hence they can get selective DOF for artistic effect. ie they want small DOF so they can use blur to concentrate viewer attention. You should not select a DSLR.All three variables of DOF work against each other. If you put the camera further away to increase subject distance you will tend to zoom in to fill the frame. ie you will increase the focal length. Increasing the focal length will reduce the aperture number and hence reduce the DOF. This is why some lenses specify maximum aperture as f3.4-5.6 for example. As you zoom out the fixed diaphram diameter divides more times into the increasing focal length. Kit lenses do make some attempt to maintain the aperture. Pro lenses typically have a cam that alters the diaphram size as you zoom in order to maintain a fixed f-stop (aperture). But this make a lens bigger and heavier and lots more expensive.So in my opinion you should choose a camera that gives you the subject distance and hence angle of view at an acceptable quality with the shortest focal length lens. That camera will typically have a small sensor (ie iPhone) or a camcorder. But avoid the bigger high end camcorders that have larger sensors. These are getting back to giving cinematographers the DOF controls they want.But unfortunately camcorders are going out of vogue even faster than point and shoot cameras.You can also stop the lens down to smaller apertures but then you have to use brighter lights if you want to avoid sensor noise at higher ISO levels.But non-pro level camcorders and iPhones don't have the many physical controls that make operation convenient. And they don't have microphone inputs.Avoiding 60fps would allow longer shutter speeds. At 60fps 1/60th sec is the longest shutter speed possible. At 30fps it is 1/30th. That's twice the light.You cannot have your cake and eat it too. Keep up the great work I recently found your channel and subscribed.

author: EEVblog
author_rank: Unknown
timestamp: August 30, 2018, 11:08:08 am
content: Quote from: TheDefpom on August 30, 2018, 09:16:43 amThere is always the 2nd hand market.My Sony NEX-GV30 for example that I use for talking head mailbags is a superb quality APSC-C sensor HD video camera with interchangeable E-mount lenses. I got it 2nd hand quite a few years ago now for under AU$1k without a lens. As I had e-mount lenses on my still camera I was good to go. There are likely plenty of good used cameras available.But as I said, a new camera isn't going to magically fix any video depth of field issue, unless you pay top dollar. You already have a DSLR with APSC-C sensor, you basically can't get better unless you get a real expensive lens, or an expensive full frame camera, but you don't want to go there for the reasons Wilfred mentioned. Maybe a used Canon HFG20 or HFG30 on the cheap, that's the camera I used for most of my videos until recently. Great internal mics, all the manual bells and whistles, and a smaller but high quality sensor and good lenses. But any of the $1000 class "pro-sumer" camcorders would do the trick, again, 2nd hand.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 11:15:12 am
content: If you think my camera sensor is reasonable then I should look at different lenses to see if I can solve it that way, should be cheaper than a new camera at least.

author: rjp
author_rank: Regular Contributor
timestamp: August 30, 2018, 11:20:29 am
content: light light and more light will help all cameras, even the best.with good light, f8 and a shorter lens, most of the scene should be in focus if you leave it in manual.if you want autofocus from closeups to distance, DSLR's arent always the best choice, their focusing is best when using the mirror, which doesnt happen on video.

author: Towger
author_rank: Super Contributor
timestamp: August 30, 2018, 11:48:20 am
content: Having read all the posts, my conclusion is also more light.

author: EEVblog
author_rank: Unknown
timestamp: August 30, 2018, 11:56:55 am
content: Quote from: TheDefpom on August 30, 2018, 11:15:12 amMore light is likely cheaper than a good lens and will give greater guaranteed benefit.But I can't help but think that a good quality flexible bench mount camera arm will work wonders for the content. It's always better to move the camera to get the right shot than move the gear.And using a fixed camera above the bench sucks for seeing scope screen and other gear including your bench meter. And given that you do a lot of repair videos, seeing the gear is important.I'll move and re-position my camera dozens of time during a typical video to get the right angle and framing.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 09:24:13 pm
content: So 3000 Lumen still isn’t enough?How bright are your lights Dave, Lumen at the bench for comparison?Obviously I am going to require them to be brighter because of the f16 setting.When I first got the camera and I was trying to get a better dof I was using f8 or so, but I saw my videos were too dark, which is when I started to increase from about the 800 Lumen my desk lights were providing, which had been adequate for the iPhone.A strong but flexible mount might be the solution for a different camera shot, as long as it doesn’t shake around it will be ok, I tried a cheaper one some time ago and it wobbled with the slightest vibrations so I scrapped that idea.I have my camera on a quick disconnect mount, which I have on my overhead rig, tripod and mini tripod, so I can remount it easier, but I am using a mains power adapter instead of a battery so the wire is a restriction, I am doing a live stream this Sunday morning at 8am NZ time whilst I try to repair a hp8901b so I will see about some different camera angles then. I do want to try and keep it over the bench (purely because of space) but a side on bench view might be possible, it just means it will be harder to use the camera and see its screen. I have tried using the hdmi output on a monitor and that was helpful, but the monitor is a bit far away as there isn’t any room to mount it by my bench.I did pick up a dual battery pack option with remote, which I intended to use but the remote only operates the photo button, not the record button argh!

author: Peabody
author_rank: Super Contributor
timestamp: August 30, 2018, 10:35:17 pm
content: I have no experience with Youtube videos and streaming, but considerable experience with photography. I'd just like to double down on some of the comments made by others. Using a larger sensor, such as full frame or APS-C, automatically gives you a shallower depth of field, which is the opposite of what you want. If depth of field is the major issue you're dealing with, something like MFT, or the even smaller sensor found in a quality point-and-shoot, would give you a greater depth of field. And remember that a 1080P video only has a 2 megapixel frame size, so resolution/sharpness isn't likely to be an issue. But the smaller the sensor, the more light you will need to get qualilty video. Increasing your ISO setting can substitute for increased lighting to some extent, particularly with modern cameras, but the laws of physics eventually get you.Actually, a quality camcorder in theory should be a pretty good solution - small sensor, good lens, extensive zoom capability. But unfortunately, most camcorders have a lens that's just too long even when fully zoomed out. You have to put them too far away to get the field of view you need.Something like a GoPro is about the right size, but the lens they have is so wide-angle that you get distortion.I honestly don't know what the ideal camera would be for this. But so many people are making these videos now that someone should come up with the ideal low-cost camera designed specifically for Youtube videos. It would have a small, high-quality sensor, zoom lens, auto-focus, good near focus, external mic jack, AGC enable/disable, and full swivel display. And I also wonder whether USB output would be more useful than HDMI - in other words, it would appear to be a webcam, with no BlackMagic converter needed, but with no loss of quality.On a side note, if you can't turn off AGC in the Canon camera, Magic Lantern may let you do that.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2018, 11:22:52 pm
content: I have just purchased a RC-6 remote which MIGHT allow me to use the remote to stop/start video... will see when it arrives.I also just purchased the flexible arm Dave suggested, so I can try mounting the camera more to the side of the bench, and still be able to move it around easily, I just hope it can take the weight of the camera, I guess I will find out.The remote is something I wanted anyway, but it will mean that the need to reach the camera is less important.If I can get a good position which works for DOF etc. then I can look at re-organising my shelving/wall to mount a small monitor which I can use to keep on eye on the camera view, the LCD just doesn't do a good enough job of being able to see the actual brightness and focus, its just too small.In the mean time I could move my fixed mount and see if I can get a better view, the only issue is that if I have the camera further away, I will need to zoom in more, which will reduce the DOF... so that may be worse, but I need to try something.

author: wilfred
author_rank: Super Contributor
timestamp: August 31, 2018, 12:35:55 am
content: There is an app called DOFmaster for the iPhone to help make sense of DOFIt is also available athttp://www.dofmaster.com/dofjs.htmlI tried plugging in a few numbers. I used a CoC circle of confusion value of 0.004mm (a number I just found on some website and didn't verify for suitability)An IPhone 6s has an aperture of f2.2 and a focal length of 4.1mm which means the actual physical diameter of the aperture is 1.86mmThe iPhone lens gives an angle of view roughly equivalent to a 28mm lens on a full frame DSLR or about an 18mm lens on an APS-C DSLRUsing the DOF calculator for an iPhone focused on a subject at 100cm the DOF was 64cm- 226cm50cm 39cm - 69cmChanging to a Canon 1000D (750D wasn't there) with an 18mm lens at f3.6a subject at 100cm the DOF was 83cm-125cm50cm the DOF was 45cm - 55cmwith an 18mm lens at f16a subject at 100cm the DOF was 52cm-1272cm50cm the DOF was 34cm - 91cmSo I hope you can see that stopping the DSLR lens down to f16 will improve the DOF but it will cost you in light loss. 4 stops plus a bit more ie you will need over 16 times the light intensity. Or you will need to go from say ISO 200 to ISO 3200.Or you could use a shutter speed twice as long, 4 times the light and double the ISO or some other combination. Or focus manually on the subject and not rely on high DOF for relatively short subject distances.The point I want to emphasise in spite of the accuracy of my figures is that the price of the camera doesn't factor into the equations. The only aspect where price might indirectly be a factor is in better low light sensor performance.The other point I want to make is that every lens regardless of how you define DOF still only focuses at one distance EVERYTHING else is OUT OF FOCUS. Just by definition. For a landscape the foreground and background merely needed to be acceptably sharp to suit the artistic intent of the photographer. But a portrait photographer will always focus on the subjects eyes. Out of focus eyes is never acceptable. It's all relative.The short focal length of an iPhone lens is simply a function of the iPhone thickness.I would say that you should focus on the subject and leave DOF to take care of the varying depth of the subject. And not the varying subject distances.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 31, 2018, 12:53:31 am
content: Thanks Wilfred, that is some extensive info.Part of the issue is that what I am doing during the video is moving around a lot, if I am fixing a piece of test gear its looking into a piece of equipment, which could be 20cm deep vertically, so for it to look OK I need that entire depth to be OK, THEN I may be working above it with my hands, so that extra height is also needed, so I need at least a 50cm DOF, and the camera was only 70-80cm above the bench (depending if you take it from the camera body or the end of the lens)If I am doing a mailbag video then I am moving around opening packages, which can be of various heights whilst doing it, and examining the item, if I could keep a fairly flat distance it would be fine but it is always moving, which is why this has been such a pain to try and get it right.I am I just trying a different camera placement now, as according to the site being slightly further away (again) will basically double my DOF, so it MAY work, the only problem is that it is screwing with my OCD as nothing is straight in the frame.... argh.

author: EEVblog
author_rank: Unknown
timestamp: August 31, 2018, 02:21:39 am
content: Quote from: TheDefpom on August 30, 2018, 09:24:13 pmNot for your depth of field obviously.This is the eternal problem of shooting indoors, it's a "low light" environment. This is especially critical for large depth of field.Quote1300 with my old install, and I think about 1700 with a new arrangement.But I'm not trying to get the very large depth of field that you are, I just have enough to get angled PCB's or products in focus.QuoteThe manfrotto ones are very stiff, should be suitableQuoteI've always used battery. Even the camcorder I use a webcam now is battery and I get about 4-5 hours operation.

author: rjp
author_rank: Regular Contributor
timestamp: August 31, 2018, 03:19:16 am
content: this is not a theoretical situation, its easily testedput your camera where you want it, set it to stills mode, manualput the aperture at f8-f11 or whatever achieves the DOF you want.set the shutter speed to the normal film shutter for your recording 1/50 -> 1/120 normally.see what the iso and light meter says.under all the automatic settings their are only 3 manual settings.. aperture, shutterspeed and iso, its well worth learning them properly and getting exact results.

author: EEVblog
author_rank: Unknown
timestamp: August 31, 2018, 08:50:52 am
content: Quote from: TheDefpom on August 30, 2018, 11:22:52 pmI miss a ton of stuff I have to annotate in the edit because I always look through the LCD when recording (usually not even at the item directly).

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 31, 2018, 09:30:06 am
content: I am always looking at the item rather than the lcd, which is something I am trying to get out of doing, as I may be out of shot or out of focus and not notice until I go to edit it, which is another reason why I want to set up a small screen to get me to look at it more often.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: September 04, 2018, 06:48:41 am
content: An update to this, I have recorded some footage with the camera slightly further away and squeezed a small monitor onto the side of my bench, that helped the DOF quite well, and I was going to use that setup instead.Today a new lens arrived, an 10-18mm 1:4.5-5.6 (the original is a 18-55mm 1:3.6-5.6), I just did some tests using this lens, and it has a better DOF when zoomed in than the original had when zoomed out (even though in theory they should be pretty much the same, at 18mm).What this change has done is allow me to lower the camera back to where it was so that I can access its controls more easily again, and using it zoomed in to 18mm I can have the aperture set to 10 or 11 (instead of 16), and it then has an ISO of 400, with what seems to be a good enough DOF.This also seems to allow my auto focusing to work better too, it changes faster from the 50% distance to the 100% distance (the bench top), if I have something really close to the camera it takes a long time to auto focus back to 100% distance, just as it did before, but it seems the DOF is within a better autofocus range so it can find it more quickly as long as it isn't too close to the camera.I have also ordered another lens a 55-250mm 1:4-5.6 which may be good for getting up really close without having to move the camera, or I may never use it for anything apart from outside stuff, I won't know until it arrives.Time will tell if this works out in the long run but it looks promising so far, it looks like I just didn't have the right lens for the job.

author: EEVblog
author_rank: Unknown
timestamp: September 04, 2018, 08:44:07 am
content: Cool, sounds like the easiest and best solution

author: EEVblog
author_rank: Unknown
timestamp: September 04, 2018, 08:48:40 am
content: Quote from: TheDefpom on August 31, 2018, 09:30:06 amI now have the wear my new glasses for looking at the small camcorder screen, as I can't see the detail any more at that short distance (about 30cm), and that's what prompted me to get my eyes checked. Don't really need them for anything else, but given that my job relies on good focus on fine stuff and short distances I needed to have them.I've considered a bigger HDMI screen attached the tripod but it's just another thing I need to keep charged and would get in the way.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: September 04, 2018, 08:53:45 am
content: I just have a crappy old 19" monitor for it, seems good enough, certainly better than the tiny LCD, you could always sit the monitor on the shelf and plug into power, and just run a long HDMI cable to the camera, that is basically what I am doing, I have a cable going to the camera anyway for the power, so I just tied them together, no extra hassle.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: September 04, 2018, 08:55:34 am
content: Also Dave, when I did my live stream on Sunday morning I showed my camera and bench setup at the beginning, about 11 minutes in or so (there is 7 minutes of nothing before I went live), in case you want to see how I have it set up, it goes through to 18 minutes.https://youtu.be/in-rBXhRp6w?t=11m17s

author: Rick Law
author_rank: Super Contributor
timestamp: September 04, 2018, 09:59:53 pm
content: To understand the trade-offs, here are some basics:Focal length:A lens casts an image of an object in front of the lens to a sensor (or film) behind the lens. Let's call the distances between lens and sensor Dsensor, and the distance between lens and the object Dobject.When the object is very far away (say, the moon), Dobjectis very very large (practically infinity). Where that image issharplycast (Dsensor) is the focal length of that lens. While this isnot the technical definition, this is the practical effect. So, if a particular lens casts the image of the moon (objects at infinity) sharply at 50mm, you have a lens of 50mm focal length.Most camera lens are really composites of a few lenses each doing a particular job to get the best effect. Some composite lens are zooms - a lens with variable focal length.Depth of Field:Depth of field is the range within which the image stays in focus. As you can imagine, when the moon is in focus for that 50mm lens, a guy standing 100 miles away is in focus also. Say as the man walk closer and closer, he stayed in focus with the moon until 50 feet away. So in this scenario, image stayed in focus (at that setting) from a range of 50-feet to infinity (~240 thousand miles). This range - the range where an image stays in focus is the depth of field.The bigger the focal length, the smaller (shallower) the depth of field.As the man walk closer, the depth of field reduces.The closer the object, the shallower the depth of field.Aperture:Now imagine if you borrowed a good (big lens) astronomical telescope say in the 1 to 3 meter focal length range... Probably, when the moon is in focus, the man 50 feet away would be out of focus. Ironically, a cheaper one (small lens) could put both the man 50 feet away and the moon both in focus.The bigger the lens opening (aperture), the shallower the depth of field.With astronomical telescopes, you typically do not have aperture control. It is always open to the max. With regular (real) camera, you typically have aperture control - the so called f-stop rather like a mechanical eye-pupil to reduce the size of the opening.The larger the f-stop number, the smaller the opening. So, one can increase the f-stop tosimultaneouslyreduce the amount of light going in and increase the depth of field. You can't just get one effect, you get both effects.As you can image, it is hard to make good big lens. So, a lens with f-stop range f2.8 to f16 would be a good bit more expensive than a lens with similar quality but with f-stop range f5.6 to f16.Smart phone camera:Typically, smart phones are thin. The camera would likely have a very short focal length. A 50mm lens (standard lens for a 35mm camera) would cast the image of the moon 50mm from the lens. To have a sensor that far from the lens would make your cell phone the size of a brick.Smart phones' thinness limits the camera lens to very short focal length. Short focal length would have great depth of field, but the image cast on the film/sensor would be smaller - resolution would not be as good as a lens with longer focal length. Note I am assuming the CCD sensor is sized to the image. Larger sensor would increase cost.Smartphones (and many digital cameras) use digital zoom instead of optical zoom. Optical zoom is the lens-glass doing the focal length adjustment. Digital zoom just crops an area of the sensor and then enlarge that area digitally to full size. Since you are cropping out some of the pixels in your sensor, you are loosing resolution. Say if the un-zoomed image of a screw is too small and you digitally zoom in to make the screw twice as long, you would be using just 1/4 of the pixels of the sensor. Smartphone with optical zoom is rare. The only smartphones I know of with optical zoom are the iPhone X and the ASUS Zenphone 3 Zoom.To reduce cost, many smart phones doesn't have real aperture control. Instead, the amount of light is controlled by shutter speed (length of exposure). In fact, you would have very limited choice of smart phone if you want real aperture control. Glaxy S9 is the only one I know of with some actual aperture control.I hope this helps with your trade-off decisions.