mitchell baum Posted October 10, 2008 Share #1 Â Posted October 10, 2008 Advertisement (gone after registration) I use magnifying glasses, strong for reading, not so strong for distance. Â How should I figure the strength I need when ordering diopter lenses for a camera? Â I don't want to wear glasses when looking in the viewfinder. Â Thanks for any help, Â Mitchell Link to post Share on other sites More sharing options...
Advertisement Posted October 10, 2008 Posted October 10, 2008 Hi mitchell baum, Take a look here How to figure Diopter?. I'm sure you'll find what you were looking for!
wparsonsgisnet Posted October 10, 2008 Share #2 Â Posted October 10, 2008 Mitchell, if you do a search you'll find lots of threads that mention this. Â Try this one: Â http://www.l-camera-forum.com/leica-forum/leica-m8-forum/61981-why-viewfinder-0-5-diopters.html Link to post Share on other sites More sharing options...
mitchell baum Posted October 10, 2008 Author Share #3 Â Posted October 10, 2008 Thanks Bill. You're always helpful. Â I also realize I posted here by mistake. Â Best, Â Mitchell Link to post Share on other sites More sharing options...
dorman Posted October 12, 2008 Share #4 Â Posted October 12, 2008 Take your camera to a store that sells cheap reading glasses. Try various dioptre strengths, looking through the viewfinder. Whichever strength gives you the sharpest view is the dioptre correction lens you need. Link to post Share on other sites More sharing options...
Marquinius Posted October 12, 2008 Share #5 Â Posted October 12, 2008 Mitchell, Â As a rule of thumb reading glasses (and I guess all glasses) are focussed on something like 75cm while your camera is focussed on something like 2 meters (top of the head and I'm sure I'm using the wrong term with "focussed") . I just asked my optician if he could calculate what I need for a diopter. Â My (reading) glasses are +2,5, my diopter is +1,25 and I'm happy with it. Â Marco Link to post Share on other sites More sharing options...
mitchell baum Posted October 13, 2008 Author Share #6 Â Posted October 13, 2008 Thanks Dorman and Marco. Â It's for a camera I haven't bought yet. But, I guess it'd be the same as for my other camera. I think all of them start with a minus 5 diopter. So I can take my current camera to the drug store and try the reading glasses. Â Best, Â Mitchell Link to post Share on other sites More sharing options...
lars_bergquist Posted October 13, 2008 Share #7  Posted October 13, 2008 Advertisement (gone after registration) Maybe I should add this piece of basic info: Dioptries are  1 divided by the focal length, in meters.  So if you have a spectacle lens or the like with a focal length of 2 meters (2000mm), then its focal length in dioptries is  1 : 2 = +0.5 dioptries  which is the focal length of the Leica M rangefinder. Negative (spreading) lenses for the nearsighted have negative focal lengths, and thus also negative dioptries. Dioptries can be added or subtracted, as required. So if your eyes are stuck at infinity, you need +0.5 dioptries correction to see the M stuff clearly. If your optical equipment—eyeballs plus specs—allows you to see sharply only at a distance of 5 meters, they add up to 1 : 5 = +0.2 dioptries, and you need to add 0.5 – 0.2 = +0.3 dioptries, because 0.2 + 0.3 make the required 0.5 dioptries.  Hence an optician (and you yourself in front of that rack with inexpensive 'gas station' specs) has only to know in respect of the Leica M, that the specs are right which allow you to focus easily on an object at a distance of 2 meters (79 inches). Also, many good optical shops have available testing sets of lenses, which you can hold in front of the M eyepiece to see which strength suits you best.  Remember however that if you go with shooting specs OR a screw-in dioptries correction lens OR a magnifyer with correction, then anything outside the finder at distances outside your unaided eye focusing range will be quite blurry. Hence my recommendation of progressive spectacles.  The old man from the Age of Bifocals Link to post Share on other sites More sharing options...
budrichard Posted October 13, 2008 Share #8 Â Posted October 13, 2008 Leica M's are -.05 Diopter(minus 0.5). Â Diopters are addative when using correction eye pieces. So if you are a zero Diopter as I am, you actually need a +0.5 Diopter(plus 0.5) correction lens to attain zero. Your Opthamologist/Optomitrist can easily perform the measurement for you and then you can do the math.-Dick Link to post Share on other sites More sharing options...
lars_bergquist Posted October 14, 2008 Share #9 Â Posted October 14, 2008 The FINDER is +0.5 dioptries, as delivered. If you can see an object at 2 meters sharply, you need no extra correction. If you cannnot, you do. I'ts no more complicated than that. Â The old man from the Age of Brilliant Finders Link to post Share on other sites More sharing options...
Shootist Posted October 14, 2008 Share #10  Posted October 14, 2008 Lars you are in error. I know that is hard to believe. All Leica M's from the M3 to the M8 are -(Minus)0.5 diopter not +0.5. From the M8 user manual (Instructions). Eyepiece Adjusted to –0.5 dptr. Correction lenses from –3 to +3 dpt. available.  The FINDER is +0.5 dioptries, as delivered. If you can see an object at 2 meters sharply, you need no extra correction. If you cannnot, you do. I'ts no more complicated than that. The old man from the Age of Brilliant Finders Link to post Share on other sites More sharing options...
SJP Posted October 14, 2008 Share #11 Â Posted October 14, 2008 The old man from the Age of Brilliant Finders AKA the old man from the age of positive rationals Never could figure out those negative number new fangled things Link to post Share on other sites More sharing options...
kenneth Posted October 14, 2008 Share #12  Posted October 14, 2008 I use magnifying glasses, strong for reading, not so strong for distance.  How should I figure the strength I need when ordering diopter lenses for a camera?  I don't want to wear glasses when looking in the viewfinder.  Thanks for any help,  Mitchell  Do you need a diopter?. I wear variofocal glasses and I am fine with my M6's which both are 0.72. In fact they are far superior at pin point focusing than my Nikon FM2n SLR ever was Link to post Share on other sites More sharing options...
Martin Schmidt Posted October 15, 2008 Share #13  Posted October 15, 2008 The FINDER is +0.5 dioptries, as delivered. If you can see an object at 2 meters sharply, you need no extra correction. If you cannnot, you do. I'ts no more complicated than that. The old man from the Age of Brilliant Finders  The finder is calculated for optimal frames in 2 meter. The finder itself has something around -0.5 diopters.  For a correction lens I would always take your correction for infinity. With that you will have a good sight from infinity to appr. 1 meter. There are just some situations where you take a picture closer than 1 meter with a M.  It is not easy to find your correction for infinity when you use magnifier. So at least you will have to ask your optometrist.  Greetings from a optometrist Link to post Share on other sites More sharing options...
christer Posted October 15, 2008 Share #14 Â Posted October 15, 2008 I like the diopter correction from Megapearls because you can change the diopter value. Â I use variofocal eyeglasses because my eyes are not as flexible as they used to be with regard to seeing things sharp at different distances. Ideally I would like to have a screw-on variofocal correction lens for my M7 but I guess that is not practicable due to the small size of the lens, and the problem with horizontal and vertical camera position. I am also astigmatic so I would love to have some correction for that too. Â Practical experience has taught me that with inflexible (old) eyes it is impossible to have a diopter correction lens that gives you 20/20 vision at all distances. I have decided that 2 meters is the most critical distance for me and have adjusted my Megapearl accordingly. Â Usually one's diopter correction requirement changes with age. No problem if you use Megapearls. Just adjust accordingly. Link to post Share on other sites More sharing options...
SJP Posted October 15, 2008 Share #15 Â Posted October 15, 2008 What I find most depressing is that no-one takes the visually challenged like myself into account (at -5.5 R and -6.5 L). I think I would like using the M8 without glasses but I have no idea how to do that. I guess there are plenty of +5 and up users out there as well. How about contact lenses? No-one on the forum seems to be using those, or are they so happy that we do not hear any complaints? Link to post Share on other sites More sharing options...
gyoung Posted October 15, 2008 Share #16  Posted October 15, 2008 Lars you are in error. I know that is hard to believe.All Leica M's from the M3 to the M8 are -(Minus)0.5 diopter not +0.5. From the M8 user manual (Instructions). Eyepiece Adjusted to –0.5 dptr. Correction lenses  from –3 to +3 dpt. available.  I tried using a correction lens, on advice from my optician I just subtracted the -0.5 from my left eye prescription and bought the nearest correction lens, it works to some extent but I have a lot of astigmatism as well which is not corrected so I dont bother normally. The optician said that even if I got a lensholder without lens (not available now?) it would be difficult to make a lens so small with my prescription, and it would have to be turned through 90 degrees for upright shots! I just make sure that the frames I get (for varifocals) are capable of being pushed back in the eye socket a bit to get the viewfinder as near my eye as possible, no problem with modern frames, the fashion is for smaller lenses but at one time it was difficult.  Gerry Link to post Share on other sites More sharing options...
masjah Posted October 15, 2008 Share #17  Posted October 15, 2008 What I find most depressing is that no-one takes the visually challenged like myself into account (at -5.5 R and -6.5 L). I think I would like using the M8 without glasses but I have no idea how to do that. I guess there are plenty of +5 and up users out there as well.How about contact lenses? No-one on the forum seems to be using those, or are they so happy that we do not hear any complaints?  Stephen  I wear contact lenses, being about -13 ish left and -15 ish right. (Spectacles would need to be a bit stronger because of the greater separation distance betweeen a spectacle lens and my own eye lens.) This corrects my distance vision. In addition I use reading glasses on top of my contact lenses because of the usual age-related long-sightedness. I find with my R8/R9 I need only a touch of diopter adjustment, without my reading glasses, and could probably manage with none at all. (I think the virtual image through the viewfinder is at 1m, and I can pretty well see at that distance without my supplementary reading glasses as well.) I'm definitely a left-eye shooter though, my right eye just doesn't seem up to things however I try to arrange things. Link to post Share on other sites More sharing options...
lars_bergquist Posted October 16, 2008 Share #18 Â Posted October 16, 2008 Lars you are in error. I know that is hard to believe. Not for me, and you're right of course. The diopter number is the inverse value, so that positive (collecting) lenses have minus dioptries and negative (dispersing) lenses have positive ... It seems that some Frenchie invented it sometime in the 1870, which just goes to show (don't ask me what). Â This old man must content himself with being able to discern between right and left. Â The old man from the Age of the Monocle Link to post Share on other sites More sharing options...
SJP Posted October 16, 2008 Share #19 Â Posted October 16, 2008 so that positive (collecting) lenses have minus dioptries and negative (dispersing) lenses have positive No just the other way around see here, Each power specification includes a spherical correction in diopters. Convergent powers are positive (ex. +4.00 D) and condense light to correct for farsightedness (hyperopia) or allow the patient to read more comfortably (see presbyopia and binocular vision disorders). Divergent powers are negative (ex. -3.75 D) and spread out light to correct for nearsightedness (myopia). If neither convergence nor divergence is required in the prescription, "plano" is used to denote a refractive power of zero. Link to post Share on other sites More sharing options...
lars_bergquist Posted October 16, 2008 Share #20 Â Posted October 16, 2008 Only harakiri remains. Â The old man Link to post Share on other sites More sharing options...
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