Quote Originally Posted by John_Nikon_F3HP View Post
Most photomic finders require a cut finder well, except for the original finder with the external CdS cell. The problem with the FTn finder is not that, but that the nameplate is different. To adapt the FTn prism for use on an earlier F that already has the cut finder well (introduced with the red dor 65xxxxx bodies), the nameplate either has to be milled, or replaced with a later part with rounded corners @ the bottom.

With respect to the focusing issue, I just checked my F2, both with its DP-11 finder, and the Tn finder that is being used as a loaner for my Nikon F, while my FTn finder is being worked on. Both finders show the correct focusing distance with the camera in the same position, focused on the same object. So, that may be a moot point. I do know that there is an issue with using F3 screens in F4's, and vice versa, which causes the focus to be off. But, F's and F2's use the same screens, unlike the F3 and the F4, which use similar screens, but slightly different.

I don't know if this helps.
On a Besseler Dual Mode Slide Duplicator, I use a
Black NASA F, equipped with a Brightscreen for an F3.
The F3 screen will fit the F, if you remove it from it's frame.

With this combination I have a choice of F2 6x mag
finder, or an original F folding prism, with built-in pop-up magnifier.

I have never witnessed any focusing problems at all.
Of course I've never focused to infinity !