Which diopter for my Nikon?

Discussion in 'Nikon' started by gallant, Aug 29, 2007.

  1. gallant

    gallant Guest


    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

    Thanks in advance for your help.
    gallant, Aug 29, 2007
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  2. gallant

    Savageduck Guest

    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, Aug 29, 2007
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  3. gallant

    gallant Guest

    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!
    gallant, Aug 29, 2007
  4. 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'.
    Nicholas O. Lindan, Aug 29, 2007
  5. 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
    Nicholas O. Lindan, Aug 29, 2007
  6. gallant

    Ken Hart Guest

    snip lots of good stuff...
    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!
    Ken Hart, Aug 29, 2007
  7. 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.
    You ellipsed out the most important part of the sentence:
    Nicholas O. Lindan, Aug 29, 2007
  8. gallant

    Jim Guest

    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, Aug 29, 2007
  9. gallant

    gallant Guest

    Man, thanks a lot guys!! I'm printing out all the great information!
    Thanks again to all who replied!!
    gallant, Aug 29, 2007
  10. gallant

    Jim Guest

    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, Aug 30, 2007
  11. gallant

    xenarshooter Guest

    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
    xenarshooter, Sep 3, 2007
  12. gallant

    gallant Guest

    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.
    gallant, Sep 4, 2007
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