Nikon FE2 won't reach infinity focus

[cptrios]

Hi all,

I picked up a Nikon FE2 last year and haven't used it all that much. One thing I noticed right out of the gate was that no lenses I mounted on it (a 50/1.8 AI-S, a 50/1.8 Series E, a 35/2.4 Series E) would quiiiite hit infinity in the split prism. I didn't think much of it because I figured it was a tiny misalignment in the mirror/focusing screen or something and that I could deal with it later. I also never noticed any issue in the few rolls I shot because they were all on Kentmere 400 pushed to 800 and therefore grainy enough to obscure any infinity sharpness issues (plus I didn't exactly shoot a bunch of landscapes).

Cut to last week, when I decided to try some Adox CMS 20 to develop in caffenol. The revelation: all three lenses cannot, in fact, focus to infinity. I have no way of being precise with this, but judging by the shots at 50mm and f/1.8, the focus distance might be around 50-60ft. So, if anyone can help me out with a couple of questions:

- Am I right in thinking that the problem is most likely with the lens mount?
- If so, is there anything I can do about it? There are a bunch of spare FE2 mounts out there on eBay and other places for $10-20, so it might be worth taking a shot at replacing it. The camera was cheap enough that I don't mind taking the hit if it's irreparable, but I definitely am not interested in spending the money to have it repaired. It's my nicest SLR, though, so it'd be lovely if there were a DIY solution!

Thanks in advance!

 

[Nitroplait]

Try to remove and reinsert the focusing screen to make sure it seats correctly. Or try to tighten the screws around the mount - as lack of infinity focus could be due to slightly longer distance from mount to film.

 

[RalphLambrecht]

Hi all,

I picked up a Nikon FE2 last year and haven't used it all that much. One thing I noticed right out of the gate was that no lenses I mounted on it (a 50/1.8 AI-S, a 50/1.8 Series E, a 35/2.4 Series E) would quiiiite hit infinity in the split prism. I didn't think much of it because I figured it was a tiny misalignment in the mirror/focusing screen or something and that I could deal with it later. I also never noticed any issue in the few rolls I shot because they were all on Kentmere 400 pushed to 800 and therefore grainy enough to obscure any infinity sharpness issues (plus I didn't exactly shoot a bunch of landscapes).

Cut to last week, when I decided to try some Adox CMS 20 to develop in caffenol. The revelation: all three lenses cannot, in fact, focus to infinity. I have no way of being precise with this, but judging by the shots at 50mm and f/1.8, the focus distance might be around 50-60ft. So, if anyone can help me out with a couple of questions:

- Am I right in thinking that the problem is most likely with the lens mount?
- If so, is there anything I can do about it? There are a bunch of spare FE2 mounts out there on eBay and other places for $10-20, so it might be worth taking a shot at replacing it. The camera was cheap enough that I don't mind taking the hit if it's irreparable, but I definitely am not interested in spending the money to have it repaired. It's my nicest SLR, though, so it'd be lovely if there were a DIY solution!

Thanks in advance!

The most likely culprit is indeed the lens mount!

 

[cptrios]

Try to remove and reinsert the focusing screen to make sure it seats correctly. Or try to tighten the screws around the mount - as lack of infinity focus could be due to slightly longer distance from mount to film.

I did try tightening the screws, actually, but I didn't want to force them. They seem tight!

I should note, by the way, that even stopped down to f/11, infinity remains out of focus. I might try another, more thorough test, though.

 

[Sirius Glass]

You might need to go to a camera repair person in the area or send it to KEH.

 

[r_a_feldman]

As Nitroplait wrote, first make sure that the focusing screen is seated properly.

It could also be that the mirror is out of position.

If it is the mount, try removing it to see if there are any spacers between the mount and the body. If there are spacers, reattach the mount without the spacer(s) and check the focus. You probably will need to experiment with different thicknesses of spacers to get the correct thickness. You can buy shim brass sheet (0.001-0.005 inches thick) from K&S Metals. I have also used 0.005” drafting mylar.

If there are no spacers but you think the lens is still too far out, it could also be that the body is distorted — not much you can do to correct that, as far as I know.

Edit: Since you think the “infinity” focus distance is about 50’, you are dealing with only a few thousandths of an inch mount deviance, so it might be possible to machine a mount thin enough to work.

 

[reddesert]

As r_a_feldman suggests, if the true focus distance is about 50 feet when lens focus ring is at infinity, for a 50mm lens, the lens is about 0.16mm too far out. Not much, but certainly out of spec. You would notice this at wider apertures (say f/5.6 or faster).

It is important to know whether the results on film agree with the focusing screen. If they do, then you can rule out the focusing screen or mirror as a source of the error. Normally, I might suspect the focusing screen before the lens mount, but if the screen and film agree ...

Do you see any tool marks on the mount screws that suggest someone has taken it apart before? Maybe someone took it apart and didn't get the pieces seated exactly right. IIRC, there are not any shims in an FE lens mount, but you have to nudge the spring for the aperture sensing ring out of the way when reassembling. The service manual has a good picture of how the pieces go together, although it doesn't show that spring.

 

[250swb]

First off infinity is not 50 feet, it is more like half a mile as regards a lens. So mount the lens and set it on the infinity stop and take a photo of infinity, not something nearby in the 50 feet region. If with a fine grain film you can see the distant telegraph pole is blurry there's something wrong with the lens or lens mount. If it is sharp then perhaps your perception of infinity needs recalibrating. If you repeat this with manual focusing and you see the telegraph pole as sharp in the viewfinder but the lens is now away from the infinity stop it's probably a problem with the focus screen.

 

[basicn]

As r_a_feldman said, it could be two things: focusing screen are not seated properly, or mirror position. Take a picture of the focus test chart or newspaper page at an angle of 30-40 degrees, under the full opened aperture and focused on marked row. When you develop the image, see if the marked row is sharp (then, everything iz ok), or if the focus is in front/behind it. If the focus is not at marked row, you can adjust the mirror by turning the mirror position adjustment screw a little (see the picture), and check that it matches infinity in the focusing screen with the mark on the lens. Be careful with that screw, you need a suitable screwdriver (picture 2). Then make again photo of newspaper and marked row at full aperture to see is it ok. You can also try a few test shots with 50 mm lens at full aperture to see is it focus on the picture exactly where you sharpened...

 

[cptrios]

Well, I finally got around to removing the mount and checking it out. In what I hope is good news, it does not sit flat on a flat surface! There are a couple of spots with a very slight warp to them, which as it turns out are actually visible with the mount still attached. Why didn't I check that out earlier? The world may never know!

I ordered a spare mount for $15, which will be an absolute steal if it ends up working. Fingers crossed.

For the record, here's a crop that shows the issue. This is at either f/2.8 or 4, with the lens focused to the infinity stop. I should actually revise my estimate of 50ft, because that telephone pole is more like 30ft away.

Also, basicn, thanks for the info about the adjustment screw. Hopefully I won't need it!

 

[ic-racer]

I don't see any shims or adjustment of the lens mount, just the specs in the service manual of 46.67 +/- 0.02mm to the pressure plate. If the camera has never been apart or dropped, maybe you are mistaken that there is a fault with the lens mount distance and should check other places of focus error.

EDIT: I see you responded with the image of the bent part while I was typing, so indeed try to bend it back or get a new on from ebay.

 

[Nicholas Lindan]

I don't see any shims or adjustment of the lens mount, just the specs in the service manual

Ah, it must be old memories of servicing Exaktas that bubbled up from my subconcious. But I have memories of removing a lens mount and finding a few paper shims underneath.

 

[Sirius Glass]

Well, I finally got around to removing the mount and checking it out. In what I hope is good news, it does not sit flat on a flat surface! There are a couple of spots with a very slight warp to them, which as it turns out are actually visible with the mount still attached. Why didn't I check that out earlier? The world may never know!
View attachment 332117

I ordered a spare mount for $15, which will be an absolute steal if it ends up working. Fingers crossed.

For the record, here's a crop that shows the issue. This is at either f/2.8 or 4, with the lens focused to the infinity stop. I should actually revise my estimate of 50ft, because that telephone pole is more like 30ft away.
View attachment 332116

Also, basicn, thanks for the info about the adjustment screw. Hopefully I won't need it!

Get out there and shovel the snow off the walk before someone slips, falls and then sues you!

 

[cptrios]

Get out there and shovel the snow off the walk before someone slips, falls and then sues you!

I wonder if that's how the mount got bent in the first place...

 

[madNbad]

I wonder if that's how the mount got bent in the first place...

Most likely dropped with a heavy lens mounted.

 

[ic-racer]

Ah, it must be old memories of servicing Exaktas that bubbled up from my subconcious. But I have memories of removing a lens mount and finding a few paper shims underneath.

Yes, a little odd. They describe checking the distance, but don't indicate what to do if it is off.

 

[cptrios]

Well, the replacement I ordered turned out to be even more warped than mine, so let’s try again!

In the meantime, does anyone have an idea of how I might try flattening it?

 

[r_a_feldman]

First, make sure that the surface of the camera body it mates to is flat.

Others might have more elegant methods, but if it were mine, I would use my rawhide mallet and a flat piece of oak board. Place the lens mount concave-side down on the board and tap the high points with the mallet. I’ve done that successfully with a front lens ring that was slightly bent out of flat.

 

[Kino]

I would suspect that if the camera took a hit hard enough to tweak the lens mount, the entire front end of the camera is now suspect.

If a stainless steel lens mount is warped, there is the real chance the underlying mount and or mirror box plate is warped as well.

With the lens mount removed you can rest the film gate on a 123 block a on a machinist's flat plate and measure the distance to the surface of the plate on all screw-hole points to see if the front has been warped.

Since the lens mount is a sub-assembly of a front plate that includes the mirror housing, there is a chance it as well is warped where it attaches to the body.

Good luck with your repair attempts!

 

[cptrios]

I know you've all been absolutely on the edges of your seats waiting to hear what happened... well, the new mounting ring seems to have fixed it! Looks like no damage to anything except the ring itself, which is great. Even with another CMS 20 stress-test, infinity is sharp. Woohoo!

 

[BrianShaw]

Good news; congratulations!

 

[r_a_feldman]

Thanks for the update. Nice to hear that you’ve got it fixed.

 

[Kino]

Good news! Glad to hear nothing else was warped.