Talk:Dioptre

message: Contact lens is currently nominated to be improved on Wikipedia:Article Improvement Drive. Please support the article with your vote. --Fenice 10:51, 16 January 2006 (UTC)
thread_title: Article Improvement Drive

message: The diopter is stated to be a non-SI unit of measurement.  Is there an SI equivalent? 142.59.153.99 19:28, 17 July 2006 (UTC)
replies: text: The SI unit for optical power is inverse meters (m-1).--Srleffler 22:43, 17 July 2006 (UTC)
thread_title: SI

message: I removed the section on converting between magnification and dioptres. It had several serious flaws:
#This "conversion" is particular to magnifying glasses and other simple magnifiers. It is not a general property. The material is better placed in the article on magnifying glasses (I will add it there). It is in fact already covered at magnification, although in different terms.
#The section (and the reference from which it is drawn) makes an incorrect distinction between magnifying power and "total power".
#The definitions given are incorrect.
#The section confuses the physical quantity (optical power) with the unit of measure of that quantity (dioptres). 
The magnification of a magnifying glass is a bit complicated. As can easily be verified by playing with one, the actual magnification ("magnifying power" or "angular magnification") of a magnifying glass depends on where you put it, and where the object is. The maximum magnification possible is obtained by putting the lens very close to your eye and moving your eye and the lens together to obtain the best focus. The object will then be typically also close to the lens. The magnifying power obtained in this condition is ¼Φ+1, where Φ is the optical power in dioptres. This is the value used for the "m×" measures of magnification. It is the maximum magnifying power obtainable with the magnifier.
Magnifiers are not always used this way, however. It is much more comfortable to put the magifier close to the object (one focal length away). The eye can then be a comfortable distance away, and a good image can be obtained very easily; it isn't very sensitive to the eye's exact position. The magnifying power in this case is roughly ¼Φ.
Interestingly, the magifying power also depends on how old you are. The factor of ¼ assumes a "standard" eye, typical of an adult. A young child obtains much less benefit from using a magnifier, because the child can obtain just as good an image by moving the object closer to her eye. The actual magnifying power experienced by the child with a lens is less.
Reference: 
--Srleffler 05:49, 28 November 2006 (UTC)
replies: text: thank you! Openlander 19:28, 28 November 2006 (UTC)
thread_title:  Magnification and dioptres 

message: I've heard dioptre measurements used in the context of Night vision - does anyone know how such measurements would be calculated? ··gracefool |☺ 02:07, 20 February 2007 (UTC)
replies: text: Dioptres are a measure of magnifying power. As far as I can see, they have no connection to night vision at all, except that a night vision system might also magnify the image.--Srleffler 04:14, 20 February 2007 (UTC)
replies: text: I often see "diopter" used with night vision devices where people are specifying the focus range of the night vision device's eyepiece (-4 to +2 Diopters, for example).  One can usually focus this eyepiece so that eyeglasses are not necessary when using a night vision device.  This makes them more comfortable to use, but the user must remember to remove and replace their glasses when switching between using the NVGs and not.WikimikeCA (talk) 18:05, 26 September 2008 (UTC)
thread_title:  [[Night vision#Biological night vision|Night vision]] and dioptre 

message: I removed some recent additions  since it was more of a how-to guide, rather than WP style, and all the text was embedded as a diagram (and thus not editable). It could possibly be useful as an article on lens clocks, if re-written in a conventional style. --Bob Mellish 06:09, 29 June 2007 (UTC)
replies: text: I missed this earlier, but in case you're still around: Wikipedia has full LaTeX math markup. See Help:Displaying a formula for information on how to format math.--Srleffler (talk) 15:17, 27 September 2008 (UTC)
thread_title:  Section on measuring dioptres deleted 

message: Conventional text doesn't offer the fonts necessary to write the mathematical equivalents necessary to describe how curvature can be used in a lens of known refractive index to give a mechanical measurement of diopters.  The necessity of .jpg files to do this seemed to be the easiest solution.  Although this approach is all or nothing, still it gives a valuable demonstration on the visual learning gleaned from how a lens clock measures dioptric power.   StationNT5Bmedia 16:25, 1 July 2007 (UTC)
replies: text: I missed this earlier, but in case you're still around: Wikipedia has full LaTeX math markup. See Help:Displaying a formula for information on how to format math.--Srleffler (talk) 15:17, 27 September 2008 (UTC)
thread_title:  Examples of how dioptric power can be measured from curvature 

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thread_title:  External links modified 

message: Section "In vision correction" currently says:
"In humans, the total optical power of the relaxed eye is approximately 60 dioptres.[4]"
This does not seem to correspond with the reference given, nor with other references I have seen.  Assuming "relaxed eye" means "minimum accommodation" (viewing infinite distance), most references give an optical power of 40 to 45 diopters. They then attribute to the crystalline lens an additional 15 to 20 diopters.
Unless I am misunderstanding the current narrative, it appears to make one or other of these mistakes: suggesting that the relaxed eye incorporates the maximum power of the lens, or suggesting that the maximum optical power is 60+20 diopters.  Gwideman (talk) 23:29, 15 October 2017 (UTC)
replies: text: The source cited does not say whether it is giving the refractive power of the relaxed eye (minimum accommodation), but a quick Google search finds other sources that do give 60 D as the optical power of the relaxed eye, with accommodation adding up to about 10 D to this, for a young adult. I didn't see any that claimed optical power as low as 40–45 D for an actual eye. Be suspicious of naive analysis based on the diameter of the eyeball. The eye is not a thin lens attached to a ball filled with air, and one over the eye's diameter is not the optical power of the eye.--Srleffler (talk) 04:07, 16 October 2017 (UTC)
thread_title:  Error? Human eye relaxed optical power  

message: Article currently says "For example, a 3-dioptre lens brings parallel rays of light to focus at ​1⁄3 metre.". Should it specify the distance between these parallel rays of light? Or am I missing something? cagliost (talk) 17:34, 22 June 2019 (UTC)
replies: text: No, any parallel rays that enter the lens will be brought to focus at the same distance. That's how a lens works.--Srleffler (talk) 03:09, 23 June 2019 (UTC)
thread_title:  Definition 

message:  Nishānt Omm (talk) 15:56, 10 April 2022 (UTC)
replies: text: Why not British English? See WP:ENGVAR for the guidelines. This article was originally created in British English, so that is what we use. Unless a topic is particular to one part of the world, we use whichever variety of English happened to be used when the article was created. --Srleffler (talk) 17:36, 10 April 2022 (UTC)
thread_title:  Why British English?