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

[Poisson Du Jour]

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.

[ic-racer]

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.

[JonPorter]

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.

[Poisson Du Jour]

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.

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.

[Poisson Du Jour]

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.

[ic-racer]

+2D correction and found it much too strong

Just remember the actual power is one more positive than indicated on the lens.

[JonPorter]

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

[Poisson Du Jour]

Let's hope the +1 lens now being ordered in is the +1 I need!

[Chan Tran]

The F3 eyepiece is smaller than the F3HP eyepiece.

[Nicholas Lindan]

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.