Talk:Magnification

message: "magnification of light(i.e. sunlight)to produce energy.where does this fit?" - edit by 70.189.159.109 to the main article. I moved it here. SeventyThree(Talk) 16:56, 22 July 2005 (UTC)
thread_title:  comment moved from article 

message: I have cobbled together a diagram (from PAR's jpgs at real image and virtual image) showing the "dimensions" of a virtual and real image. This is a first draft, so I present it hear for comment before adding it to the article (if we agree it's useful). So comments welcome, but remember this took time and effort, so please be nice :-) ...  and no, I don't know how to make SVGs --Redbobblehat (talk) 23:28, 12 March 2009 (UTC)
replies: text: Hi RBH, this looks like a great diagram.  Sounds like you've already been nagged about SVGs, but really they are astonishingly more useful thanks to the ease of editing and resizing.  Have you tried Inkscape?  It's a highly intuitive and easy-to-use free SVG-editing program.  I've made tons of diagrams for WP with it.  There's some helpful information on using it with Wikipedia/Commons at Commons:Help:Inkscape. Moxfyre (ǝɹʎℲxoɯ | contrib) 20:37, 12 June 2009 (UTC)
replies: text:  As there have been no objections in nearly 2 years, I've moved this diagram into the article. --Redbobblehat (talk) 19:48, 4 February 2011 (UTC)
thread_title:  reference diagram 

message: I have also tried to rewrite the "photography" paragraph to make it clearer. Not sure if I succeeded though; it's basically all about sign conventions ... perhaps a section entitled "sign conventions" would be better ?
* Photography: The image recorded by a photographic film or image sensor is always a real image and is usually inverted. When we measure the height of an inverted image using the cartesian sign convention (where the x-axis is the optical axis) the value for hi will be negative, and as a result M will also be negative. However, the traditional sign convention used in photography is "real is positive, virtual is negative"Sidney F. Ray Applied Photographic Optics: Lenses and Optical Systems for Photography, Film, Video, Electronic and Digital Imaging, Focal Press, 2002, , p.40. This means that in photography: Object height and distance are always real and positive. When the focal length is positive the image's height, distance and magnification are real and positive. Only if the focal length is negative, the image's height, distance and magnification are virtual and negative. Therefore the photographic magnification formulae are traditionally presented as:
::M = {d_i \over d_o} = {h_i \over h_o} = {f \over d_o-f} = {d_i-f \over f} 
--Redbobblehat (talk) 23:35, 12 March 2009 (UTC)
replies: text: After nearly 2 years without objections, I have moved this version into the article. --Redbobblehat (talk) 20:01, 4 February 2011 (UTC)

text: I'm not sure if the sentence "Only if the focal length is negative, the image's height, distance and magnification are virtual and negative." is helpful here. I think it helps to clarify the point about sign convention, but AFAIK a camera lens with negative focal length would not produce a usable image ... ie no photographic lens system would have a negative focal length! Comments welcome --Redbobblehat (talk) 20:01, 4 February 2011 (UTC)

text: I also considered adding some guidelines for using the formulae in close focusing applications. Specifically : to measure d and d' from the front and rear nodal points of the lens - which are not easy to locate, and pointing out that when focused at infinity, (d'-f)/f = 1/f. I hesitate because I'm not sure that this article is the correct place to provide such detail. Comments welcome --Redbobblehat (talk) 20:01, 4 February 2011 (UTC)
thread_title:  sign convention 

message: The article lists telescope angular magnification as f_e/f_o. But since f_o > f_e in telescopes, that results in a magnification of <1! That makes no sense to me. These facts about magnification need citations, anyway. PenguiN42 (talk) 00:45, 15 May 2010 (UTC)
thread_title:  Telescope angular magnification 

message: This was moved here from the main article where it was posted by user:Robert M Dewey:
:Consider who your readers are what what they may want to know. Some like me want to know the basic concepts not the mathematics. What are concave and convex lenses? Does one magnify and the other minify. Which lenses does one use to make a telescope -- concave or convex or one of each or what? can you do this by holding each lens with your fingers? These are not childish questions. They get at the underlying concepts of the physics of optics. The technical mathematics is good too. But don't forget that if you can't explain the basic facts underlying the mathmatics of optics simply, you probably only know the mathematics by rote. I came for a simple explanation of how magnification and minification works. I'd provide the information myself if I knew it. But that's what I came to your article to find out. It isn't there.
He's got a point. Man with two legs (talk) 09:42, 28 May 2010 (UTC)
replies: text: I've now added a section Examples of magnification. Man with two legs (talk) 10:10, 28 May 2010 (UTC)
thread_title:  Comment transferred from the main article 

message: There are no informations about the Magnification of Curved mirrors. Though, they sell with Labels from ~"2x" to "7x" in stores. Can anyone give information about how this is calculated? --Itu (talk) 02:51, 26 November 2010 (UTC)
replies: text: Agreed, this article needs to have some discussion of curved mirrors. 75.37.70.77 (talk) 16:58, 3 May 2011 (UTC)
thread_title:  Curved mirror 

message: In optics, does "unit magnification" simply mean M=1, or is there more to it than that ? Redbobblehat (talk) 18:32, 4 February 2011 (UTC)
thread_title:  Unit magnification  

message: Currently the article states :
:*Angular magnification — For optical instruments with an eyepiece, the linear dimension of the image seen in the eyepiece (virtual image in infinite distance) cannot be given, thus size means the angle subtended by the object at the focal point (angular size). Strictly speaking, one should take the tangent of that angle (in practice, this makes a difference only if the angle is larger than a few degrees). Thus, angular magnification is given by:
:::MA = tanE' / tanE
::where E is the angle subtended by the object at the front focal point of the objective and E' is the angle subtended by the image at the rear focal point of the eyepiece.
My first question is : why measure angular object size (E) about the front focal point and not the entrance pupil ?
: My guess is : it's just plain wrong - the "view" of anything rarely has anything to do (directly) with the focal or cardinal points ... it should say "Where E is the angular size of the object (the angle subtended by the object at the centre of the entrance pupil) and E' is the angular size of the image (the angle subtended by the image at the centre of the exit pupil)". -- Redbobblehat (talk) 21:09, 11 February 2011 (UTC)
replies: text: My guess is that under paraxial approximation, E' / E is "close enough to" tanE' / tanE, so in first-order optics angular magnification is usually given as = E / E' (Hecht 2003 Optics p.210). If so, perhaps it should state that "Whilst transverse magnification, M = tanE' / tanE, for calculations using paraxial approximation (where neither E or E' are more than +/- 10° from the axis) we can get away with M = E' / E". --Redbobblehat (talk) 21:09, 11 February 2011 (UTC)
thread_title:  angular magnification 

message: The article discusses linear magnification and angular magnification, but not the magnification of the virtual object that occurs when the virtual object isn't at infinity. In terms of being able to see detail with a magnifying glass, angular magnification is what matters since the angular resolution of your eye is limited. However, this doesn't answer the question "How much bigger does the thing behind the magnifying glass appear to be?" If you hold a magnifying glass one focal length from your subject and look through it, the object appears to be at infinity in terms of focus accomadation and stereo vision, so the virtual object size is infinite. If you hold that lens to your eyes, the angular magnification is unity, but the object still appears to be infinitely big even though the images on your retinas look the same -- its' just that your eyes are focused and converged to infinity so it looks infinitely far away. If the object is less than one focal length from the lens, then in terms of accomidation and vergence, the object appears to be closer than infinity, so the virtual object height is finite. In the limit that the lens is on the object, it has no effect.
So: What's the formula for virtual-object magnification as a function of eye-lens distance, lens-object distance, and lens focal length? I don't see it here and there are no equations on virtual image. —Ben FrantzDale (talk) 13:19, 2 December 2011 (UTC)
thread_title:  Virtual-object magnification? 

message: It might be helpful for there to be included a reference chart of what you can see at what magnification. (that's why I came to the page) For example you could say at X magnification you could see cells and at Y magnification you can see molecules or individual strands of dna or some such. Drewder (talk) 22:31, 19 February 2015 (UTC)
thread_title:  Scale