F4 diopter adjustment doesn't work, how to fix.

Last spring I picked up an F4 from Japan. Overall I'm pretty happy with the camera. Everything seems to work well except for the Diopter adjustment wheel. It is stuck and will not move when I try to pull it out. Is this an easy fix (I'm fairly handy) or should I just forget about it and just take pictures. I will mostly be using AF lenses, but I do have MF lenses that I want to use The focus confirmation light works so if the screen is off because of my refractive error I should be able to confirm focus with MF lenses. Also the LCDs in the finder seem to be ok and there is not much LCD bleed, not enough to make a difference. I have been shooting Nikon since '68 (Nikkormat FTN), F ftn, F2, FM2n, FE2, FA, only the FA remains along with the F4 and D7100 and D600 plus a boatload of lenses.

It should be repairable, the DP-20 viewfinder is easy to open and the place with the diopter drive is accessible.



See (also for disassembly):

Thanks for your quick response Andreas. Is there any way to finesse this without removing the finder cover? The wheel remains immovable and I am afraid of pulling too hard to loosen it up. I think that I could get the cover off, but how to free it up once I get the cover removed. Have you ever had an F4 that couldn't adjust the diopter? Since I went digital with the diopter adjustment I have gotten used to focusing without my glasses. The adjustment on my F4 seems to be for normal vision and when I focus with my glasses on the screen appears sharper and I can see the corners of the screen with my glasses. The F4 seems to have a High Eye Point viewfinder.

Robert Ley said:

Is there any way to finesse this without removing the finder cover? The wheel remains immovable and I am afraid of pulling too hard to loosen it up. I think that I could get the cover off, but how to free it up once I get the cover removed.

Click to expand...

I don't think it can be repaired from the outside, as I suspect the drive is jammed. The only way to fix this is to take it apart.

I would open the viewfinder, check where the problem is and if it can't be repaired, reassemble the viewfinder.

Robert Ley said:

Have you ever had an F4 that couldn't adjust the diopter?

Click to expand...

No, but I have a DP-20 where the viewfinder cover doesn't move. This should be fixable, but it will require disassembly too.

Robert Ley said:

Since I went digital with the diopter adjustment I have gotten used to focusing without my glasses. The adjustment on my F4 seems to be for normal vision and when I focus with my glasses on the screen appears sharper and I can see the corners of the screen with my glasses. The F4 seems to have a High Eye Point viewfinder.

Click to expand...

Yes, it's an HP viewfinder. I use it with my progressive lenses. But I prefer it without glasses, as they do limit the viewfinder image somewhat.

If I can help you from a distance to open the viewfinder, I'd be happy to do so here in the thread. Anyway I think my post (first link) should cover everything important.

Robert Ley said:

The F4 seems to have a High Eye Point viewfinder.

Click to expand...

The Multi-Meter Finder DP-20 is the Nikon F4(s) standard finder and highly recommend as it optimizes performance of the F4. It offers a high eyepoint of 22mm and virtually 100% picture frame coverage.

Click to expand...