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  1. #1
    Michel Hardy-Vallée's Avatar
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    Nikon FM eyepiece diopter confusion

    I'm not terribly short-sighted, but I thought I might put all chances on my side by ordering a diopter eyepiece for my Nikon FM2n.

    My prescription for the right eye is +0.5 sphere. The astigmatism is rather low (-0.5 cylindre), so I don't take it into consideration.

    Logically, I told myself, I will use the Nikon +0.5 diopter eyepiece. They say that +0.5 is the combined lens/finder dioptry, so I reason that it means that the entire camera optical system between my subject and my eye is equivalent to +0.5. Lucky me, I need +0.5 in my right eye to see properly. That's what I have in my glasses.

    Now here's the catch: I bought the eyepiece, put it on my FM2n, and in fact it makes viewing worse. I checked very carefully again and again, putting the camera on a tripod and not touching the focus, and still, it looks worse with the eyepiece correction.

    Did I make the wrong calculations based on my prescription? Or is it just the case that my brain is not used to the corrected view, so he has a hard time processing the new visual data? I fail to see how the fact that the viewfinder is -1.00 by default has anything to do with my problem.
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

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  2. #2

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    My reading glasses are +2.0 and I have a 0 diopter (a 0 diopter is actually a +1 lens, not the one that came with the camera) and it's good. The reason is that I need a +2 to see at 12-15" but I only need a +1 to see at 39" (or 1 meter) that's what I need to add to the viewfinder.

  3. #3
    Steve Smith's Avatar
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    If your prescription is positive then you are long sighted, not short.

    So if you are actually short sighted rather than long, the -0.5D lens may have worked.


    Steve.

  4. #4
    Michel Hardy-Vallée's Avatar
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    Oh, sorry about the vocabulary error. I'm long-sighted then! My prescription glasses are working correctly. The confusing thing is that my left eye is short sighted (- 0.5) and my right eye is long sighted (+ 0.5). I have a different degree of astigmatism in either eye, mostly concentrated in the left one.
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

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  5. #5

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    Michel -- I tried to figure this out for myself, but finally just asked my eye doctor. He wrote the diopter correction down on a piece of paper for me, and I've been OK ever since.
    Jeff Polaski
    "A full-time job seriously interferes with photography."

  6. #6
    PhotoJim's Avatar
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    Ask your optometrist for the diopter you require at a viewing distance of 1 metre. That's the diopter that you will require.
    Jim MacKenzie - Regina, Saskatchewan, Canada

    A bunch of Nikons; Feds, Zorkis and a Kiev; Pentax 67-II (inherited from my deceased father-in-law); Bronica SQ-A; and a nice Shen Hao 4x5 field camera with 3 decent lenses that needs to be taken outside more. Oh, and as of mid-2012, one of those bodies we don't talk about here.

    Favourite film: do I need to pick only one?

  7. #7
    Michel Hardy-Vallée's Avatar
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    Quote Originally Posted by PhotoJim View Post
    Ask your optometrist for the diopter you require at a viewing distance of 1 metre. That's the diopter that you will require.
    Ah... That's something I did not think of. As I said, I'm actually long-sighted in my right eye, so I need correction for reading up close. My glasses are doing a good job, so I was thinking that the same correction would suffice.
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

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