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Photo Forum / Film Photography / 35 mm / September 2007Which diopter for my Nikon?
Hello, I hope you can help me out. I'm nearsighted, wear eyeglasses, -1.75 prescription. Which strength diopter do I need to buy for my Nikon FM camera? Thanks in advance for your help. > Hello, > [quoted text clipped - 3 lines] > > Thanks in advance for your help. There are a number of issues here: A -1.75 dp correction should be available. What you should be aware of is, this will give you your corrected vision of the World through the VF. However when you move your eye from the VF you will be reduced to your near sighted Mr. Magoo view without your glasses. If you wear contacts ( for average miopia a good way to go) you will not need a VF corrective lens and be able to adjust with the dioper adjustment found all Nikon DSLRs. Do you have the same correction for both eyes? If not you might have to get the appropriate lens for your shooting eye. Do you have any astigmatic correction? If you do, as I do in a severe way, you are better off just working with your glasses on as the sphero-cylindrical or toroidal lens has to be aligned on the correct axis to provide the proper correction. This is difficult to achieve with an add-on lens or contacts and is best fixed with good old glasses. -1.75 dp is not a massive correction and if you are able to accomodate (focus) without your glasses you might be able to make do without a diopter corrective lens. Otherwise I would try a 4 step range from -1.0 to -2.0 and see what works best for you. Then If you want to make the truly radical fix, there is laser surgical correction, which works pretty well for miopia. Good luck, Savageduck  Signature π 4 ∑∆ > > Hello, > [quoted text clipped - 35 lines] > -- > ? ? 4 ?? Hey, thanks a lot for your informative reply. I really appreciate it! With glasses, it's not that big of a deal to work with the camera but I just thought it'd be cool to look throught the VF with my naked eye. I'm still learning photography with my 35mm Nikon. I guess I can also use the split image rangefinder spot for focusing, even without my glasses. ;) Thanks again! > I'm nearsighted, wear eyeglasses ... -1.75 ... > Which strength diopter do I need to buy for my for my Nikon FM The obvious simplistic answer is a -1.5 or -2.0. However ... Nikon's are set to make the screen appear as if it is 1 meter away with no correction lens - in a sense they are already set at -1.0 diopter. To confuse things a Nikon +1 diopter is marked as '0' correction because the total correction of the system is now 0 diopters at infinity focus. You won't find a '-1' diopter lens - if that is what you want it is called a 'replacement eyepiece' and is a flat piece of glass. To view the screen without glasses the optimum is the correction you need for 1 meter vision and this is probably less correction than your normal eyeglasses. Your eyeglass prescription is for ~5 meters to infinity - about the distance from the chair to the chart at the optometrist. So you may be happier with a -1.0. A -1.0 is, naturally, marked '-2'. To help settle or further confuse the issue you might want to give your optometrist a call and see what he advises. There is a flip side to all this: wearing glasses you are now far-sighted and are most comfortable viewing at infinity. So with glasses you may find a +1 diopter (marked '0') works best - this moves the screen from 1 meter apparent distance to infinity. I made the switch to a '0' diopter lens about the time I started having to use another set of eyeglasses for reading and computer work. Focusing at 1 meter with infinity correction in the eyeglasses was a strain - having the screen at infinity was far more comfortable. I find this holds with bifocals as the greatest and best corrected area of the lenses is the upper half that is set for infinity. The less focusing strain on the eye the better one can focus - so there is more than just a comfort issue. I would advise evaluating the correction lens late in the day. In the morning my eye accommodation is not so bad; late in the evening it is terrible. Go for the one that is the most comfortable and relaxed for the eye, this may not be the one that gives the illusion it is the 'sharpest'. SignatureNicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/index.htm n o lindan at ix dot netcom dot com > "gallant" <dskgallant@yahoo.com> wrote > > I'm nearsighted, wear eyeglasses ... -1.75 ... > > Which strength diopter do I need to buy for my for my Nikon FM > [much blather, deleted] There is a simple answer: Without your glasses find your most comfortable viewing distance. If the range is broad then try for 1/2 way from things coming into focus to things being too near. Take the inverse of the distance in meters - this is the eyepiece lens you need. Since there are only a few choices an alternative is to, without glasses, view something 1/3 meter (33cm / 13 inches), 1/2 meter (50cm / 1 foot 8 inches) and 1 meter (3 feet 3 inches) away. Pick the least worst: 1 meter Do nothing 1/2 -2 1/3 -3 SignatureNicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/index.htm n o lindan at ix dot netcom dot com > There is a simple answer: > [quoted text clipped - 13 lines] > 1/2 -2 > 1/3 -3 I have a followup if you don't mind.... I understand what you're saying but when I'm testing, as per the above, at home, what object(s) should I be looking at from 1m, 1/2m and 1/3m away? Thanks again. snip lots of good stuff... > I would advise evaluating the correction lens late in the day. In the > morning my eye accommodation is not so bad; late in the evening > it is terrible. Go for the one that is the most comfortable and > relaxed for the eye, this may not be the one that gives the illusion > it is the 'sharpest'. Very informative, thank you! But I am curious about your last sentence: "comfortable and relaxed.... may not be ...the 'sharpest'." I would think that for the most critical focusing, you would want the corrective lens that makes the image 'snap'. On my studio cameras, I use my reading glasses to focus/compose on the ground glass, then I pop up the magnifier to get critical focus (without the reading glasses). The magnifier, while not a comfortable viewer lens, gives a sharper image. I completely agree with the "late in the day" part. My local newspaper is an afternoon one, and by the time it arrives, reading it gives me a headache. Of course that may be their editorial slant and not my eyes! > But I am curious about your last sentence: "comfortable and relaxed.... > may not be ...the 'sharpest'." I would think that for the most critical > focusing, you would want the corrective lens that makes the image 'snap'. The highest resolution I can have of an object is at the nearest point of my eye's accommodation. However, the associated eyestrain soon mitigates any advantage as I can't hold this position for long. My optometrist cranks the correction up until I say "That's the sharpest" and then he turns the correction back an ooch. At first I think that this is less sharp but looking at the eye chart I can read last line just as well and it feels relaxed and natural. > be ...the 'sharpest'." You ellipsed out the most important part of the sentence: > be >>> the one that gives the _illusion_ it is <<< the 'sharpest' SignatureNicholas O. Lindan, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/index.htm n o lindan at ix dot netcom dot com > Hello, > [quoted text clipped - 3 lines] > > Thanks in advance for your help. Go to the photo shop and try some out. There isn't a -1.75 diopter lens. You will need to decide which one works best for you. You might get by with no help. Jim Man, thanks a lot guys!! I'm printing out all the great information! Thanks again to all who replied!! > Man, thanks a lot guys!! I'm printing out all the great information! > Thanks again to all who replied!! FYI, if the built in eyepiece is -1 diopter, then what you would need is a -.75 diopter. I'll bet that a -0.5 diopter would work fine. Jim > Hello, > [quoted text clipped - 3 lines] > > Thanks in advance for your help. I have had the same dilema and still do. It would cost about $80 to get a correction lens made for my Pentax K2 and fit into an eyecup frame but it could be done. You have to know the diopter for the viewfinder, my K2's is -0.80 or so, my perscription for my right eye is -1.25... so I need a lens of -0.45 diopter. And you simply subtract one from the other, 1.75 minus 0.90 (viewfinder) = -0.85 for you ... that is if* -0.90 is the diopter of your viewfinder, you should be able to find that in the owner's manual or http://www.nikon.co.jp/ in the history section or http://www.butkus.org/chinon/ for the manual in pdf, if he has it there. After further checking ... it looks like the FM's viewfinder is -0.86 diopter so 1.75 - 0.86 = -0.89 ... a -1.00 would probably work unless you can find a -0.90. maybe find a focusing screen with a little bit larger of a circular microprism. Which is what I've come to rely on... and now starting to try rangefinders! SignatureGiant_Alex not my site: http://www.e-sword.net/ |
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