Dioptric correcton lens +1.0: Nikon F100 & Pentax 67 interchangeability?

Discussion in 'Medium Format Cameras and Accessories' started by Poisson Du Jour, Dec 12, 2011.

  1. Poisson Du Jour

    Poisson Du Jour Subscriber

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    Somewhere I have picked up information (Pentax forum??) that the dioptric correction lens that fits a Nikon F100 (probably others) is a direct exact fit for the Pentax 67 viewfinder bezel? Can anybody shed light on this and advise of actually fitting from F100 to 67 without modification? It seems to me correction lenses for the F100 are more widely available than those for the 67. Ta. :smile:
     
  2. ic-racer

    ic-racer Member

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    I know the Nikon ones fit the Bessa cameras. Just remember the actual power is one more positive than indicated on the lens. So, if you need a "-3" use one marked "-4" if it is not going on a Nikon.
     
  3. JonPorter

    JonPorter Member

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    Sorry, no. The Pentax 67 standard prism eyepiece is slightly larger than the F100/HP eyepiece. And I assume the Pentax meter prism eyepiece is the same size as the non-meter prism's.
     
  4. OP
    OP
    Poisson Du Jour

    Poisson Du Jour Subscriber

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    I have the Pentax TTL prism. Just now I've unscrewed the eyepiece and heading off the Sin City to bootscoot 'round the favourite haunts for a possible lens from a Nikon eyepiece. Separate communication in the last 24 hours has strongly indicated there is a known workable match with one of the Nikon lenses, if not for the F100. Which one of several if what I'm setting out to establish today.
     
  5. OP
    OP
    Poisson Du Jour

    Poisson Du Jour Subscriber

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    Back in studio again, I can confirm the following, for others who may be interested.
    The eyepiece dioptric correction lenses for Nikon F3, F3HP are an exact fit for the Pentax 67 TTL prism (probably other finders too). I came back with a +2D correction and found it much too strong (out of focus), so stepping back to +1.0.
     
  6. ic-racer

    ic-racer Member

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    :wink:
     
  7. JonPorter

    JonPorter Member

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    Glad you found a match. But F3 eyepieces won't work. They're smaller than the F100's.
     
  8. OP
    OP
    Poisson Du Jour

    Poisson Du Jour Subscriber

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    Let's hope the +1 lens now being ordered in is the +1 I need! :pouty:
     
  9. Chan Tran

    Chan Tran Member

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    The F3 eyepiece is smaller than the F3HP eyepiece.
     
  10. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Nikon uses two thread sizes for the eyepiece - TTBOMK the F3 and the F3HP take different sizes, which may be the cause for some of the confusion. Nikon makes an adapter that goes between the sizes, though the adapter is meant for right-angle finders. There are also two flange diameters - sometimes you can get an eyepiece that fits [screws in] only to find it won't let you open the camera back.

    Nikon viewfinders are set so the screen looks like it is 1 meter away with a flat glass eyepiece - or '-1' diopter. A eyepiece marked '0' is actually a +1 lens that with the finder's -1 makes 0 - and so the screen looks to be at infinity. A lens marked +2 will actually be a +3, when mounted to the finder the combination is +2.

    I am nearsighted but keep '0' marked eyepieces on my Nikons. Normally this would be a correction for a farsighted person. But with age my eyes have lost their accomodation and with my glasses on I find I am now farsighted - so a '0' lens makes perfect sense.
     
  11. Chan Tran

    Chan Tran Member

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    Yes I have the 0 diopter on my F3HP which is really +1 diopter lens. Now I need the +1 diopter as my eye has gone worse.
     
  12. carioca

    carioca Member

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    Reviving this old thread, because that's about all I found on diopter correction lenses for Pentax 67...
    I'm trying to find a +1 diopter correction for my Pentax67, impossible to find new or used, but it seems Nikon F100 diopters have the same diameter and are still available. I have unscrewed my standard, original Pentax eyepiece and it is plain flat glass. Considering the fact mentioned above, would this mean a Nikon 0 glass (being an actual +1 correction) would result in a +1 correction on my Pentax, since it does not have this -1 focus setup.
    Edit: Is a marked Nikon 0 diopter eypiece the same as the non-marked original Nikon one, both +1?

    Thanks for any help on this topic,
    Sidney
     
    Last edited: Jul 7, 2017
  13. macfred

    macfred Subscriber

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    A very good explanation for the Nikon eyepieces !
    On a side note - I use eypieces from the FA-,FM-, F2 - series marked -2 for my FUJI GA645 and GW670iii.
     
  14. macfred

    macfred Subscriber

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    Found this (for Nikon eyepieces with Nikon cameras):

    refractive error : +4 +3 +2 +1 0 -1 -2 -3 -4 dpt
    eyepiece : +3 +2 +1 0 -2 -3 -4 -5 dpt

    Nikon F, F2, F3, FA, FE and FM - series = 19mm
    F3HP = 22mm
     
  15. carioca

    carioca Member

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    Thanks for the information, Macfred!

    I will go for a 'marked' 0 eyepiece then, hoping it to be a +1 for the Pentax.

    Sidney
     
  16. jgoody

    jgoody Subscriber

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    Have used Nikon diopters on OM and Canon RF (with mods) and can confirm the 1 diopter offset from what's marked on the diopter.