Focusing issue, Nikon F2

[Loren Sattler]

I printed a couple of test photos to check close focusing of my Nikon F2. I did the testing because I felt some recent portraits that were shot with a 50mm lens, close up, were not as sharp as I expected.

See scans below of test photos taken at full aperture, close range with a 50mm F1.4 Nikkor lens and 75-205mm F3.8 Vivitar zoom lens (zoomed to 205mm). You will note that the plane of focus is past the cross hair target written with a sharpie on news print slanted 45 degrees away from the camera.

I have owned this camera since new. It has been serviced only once in its life (about a year ago) for an issue with the shutter and a non working meter. I have never attempted any macro work with this camera that would have certainly revealed any focus issues.

Can someone offer advice here? Is this an abnormal amount of focus error? Does the camera need an adjustment? When firing the camera with the lens off, the viewing mirror appears to act normally. Where on the camera would an adjustment be made?

Thanks in advance for the help.

 

[Loren Sattler]

Clearer scans here:

 

[MartinCrabtree]

If it doesn't show up when viewing only in photos I suspect the film isn't held flat.

 

[John Koehrer]

Focusing screen seated correctly? You've used it for years so I suspect it is.
There are only two things in the body that cause shift.
Focus screen and the rest position of the mirror.

I've seen one camera that had a broken casting but was held together by the leatherette. That's
likely not your problem though.(cough)

I've seen focusing rings on lenses slip or incorrectly adjusted.
I'd check the focus at the film plane with a ground glass or frosted tape. Not on the film rails but between them.
IF the focus is sharp on the GG take a look at the distance scale to see if it indicates the proper distance.

 

[cooltouch]

I own a couple of F2s and have never experienced this problem with either of them. But I also own a Pentax LX and I just had it serviced. The main reason why I had it serviced was because focusing was way off. If I focused on a subject that was 10 feet away, the lens scale would read about 25 feet. Visual inspection of the mirror at rest did not reveal any issues. It must have been something internal. Anyway the tech was able to fix it, whatever it was. So I recommend you check it at the film plane as John K explains and take it from there. Make sure the focusing screen is intact and correctly seated and also make sure the pentaprism isn't loose or shifted inside the finder.

 

[MartinCrabtree]

How could the focus screen effect focus at the film plane as pictured? Honest question I've thought about this and got nothing.

 

[Loren Sattler]

The focus screen on a Nikon F2 is removable. They sold a variety of screens for specialized applications. The standard one offered both split image and fresnel style focusing. I used the split image feature when taking the test photos.

If the screen is not seated properly in its mount, it would shift the indicated focus in the view finder and cause a focusing error. The other potential issue could be the mirror. If the mirror is not seated properly (at its 45 degree angle), that could also cause a focus error.

The distance from the mirror to the screen must equal the distance from the mirror to the film plane for the reflex system to indicate proper focus in the viewfinder. It is no different than the set up in for the top lens in a TLR camera except there the mirror is fixed and does not move like in an SLR.

Hope this helps.

 

[Loren Sattler]

Here is an update. I sent an inquiry to Midwest Camera Repair in Michigan about this issue (they have done my repairs in the past). They advise that film SLR's do not have any adjustment for focus. They are fixed at the factory. The exception is for infinity focus. Somehow there is an adjustment for focus to be on infinity when the lens hits the stop.

That suggests to me that any error in the focusing mechanism in an SLR is intended to be corrected with depth of field provided by the lens.

 

[MartinCrabtree]

I still believe the issue is at the film plane. While we're at it a question for Loren. When taking the photos posted was the newspaper parallel to the film plane? If not it may simply be an issue of depth of field at large aperture.

 

[Loren Sattler]

news print slanted 45 degrees away from the camera

See "slanted 45 degree" comment in original post.

 

[mdarnton]

They are wrong about film cameras. When you get the camera back, lift the mirror and look under the right front edge for a stop. The stop will be adustable. Back focus is the common problem, and it means that the mirror over the years has hammered the stop downwards.

When the mirror stop has moved downward, the lens to mirror distance is increased. To compensate, you focus the lens a bit back farther inwards. While this makes the image on the ground glass finder in focus, it makes your focus slightly behind the film, resulting in back focus in your photos.

If you have prime lenses and they haven't been messed with, then infinity will accurately be infinity, and you can use one to set the stop. The reason you notice this at infinity is because you can't focus the lens inwards past the inifinity setting. Find something that's really at infinity; notice how the lens won't quite focus on it. If you adjust the stop upwards, you will be able to focus at infinity. If you're timid, stick a piece of tape or two on the bottom corner of the mirror there, and notice the effect it has on infinity focus.

The usual adjustment is some sort of cam, where a very tiny movement will do quite a bit, so move in the tiniest increment you can manage to adjust this. Some cameras just have a finger you can bend. My Nikon FGs have a cam with a X on it for a screwdriver--it looks like a big funny flat screw head. On my N90 it's just a not-special-looking eccentric screw that takes a small allen wrench, so you might find something more like that.

 

[Loren Sattler]

mdarnton, I believe you have answered the puzzle! My mirror stop does have an adjustment screw. I can see where the mirror contacts the stop and there is paint removed (and therefore probably some wear) that could account for the focus error. A photo of the mirror stop is below.

Gee, this certainly has me losing confidence in the repair company. Note, I did not send them the camera. I sent them this post and asked for their opinion. Their response is very lame. How could they not know this? They have been in business for decades.

Thanks for the solution.

 

[mdarnton]

You will not believe how little you need to turn the screw to have an effect! I think the one in the front is eccentric and the one to turn--that tilts the lever pivoting on the other screw.

 

[Loren Sattler]

To be fair, I am posting the dialogue with the repair outfit. Perhaps my interpretation of their response is in error. Loren

First response to my question is below 3/27/2016:
We can’t tell from your image if the amount is correct, our angle charts are different and have a scale on this so we can tell the amount of correction. Also the angle charts are for digital cameras and lens because the focus is much more critical on digital then film and they are not adjusted at a different distance then film.
Film cameras and film lens are adjusted to infinity (digital camera and lens are not). There is no micro adjustment on film lens or bodies only infinity.
Midwest

My follow up question is below 3/28/2016:
Thanks for the response. If I fully understand your answer, you are saying the camera is not built with a method to adjust the focus plane. Therefore, any error should be minor enough that depth of field in the lens takes care of it in the image.
Please confirm if my assessment of your response is accurate.
Thanks,
Loren

Their response to my follow up question 3/28/2016:
Film equipment is built with a method to adjust but only to infinity, there is no fine focus adjustment or adjustment at different focal lengths, the adjustment are all mechanical, film does not see focus error as much as digital because film has way less lines of resolution.

With digital bodies you have fine electronically adjustment for usually at 1m or 1.5 meters depending on the manufacture. With digital lens you have fine electronically focus adjustment at different focal lengths, some zoom lens are fine adjusted at 5 different spots in the zoom range.

Midwest

Below is my original email question to them 3/27/2016:
In the past two you serviced my Nikon F2 (serial F2 8015155) twice, once for an issue with the shutter and the other a dead light meter. I now wonder if I have a focusing issue and if so, what can be adjusted to correct it. Here is my story.

I printed a couple of test photos to check close focusing. I did the testing because I felt some recent portraits that were shot with a 50mm lens, close up, were not as sharp as I expected.

See scans attached of test photos taken at full aperture with a 50mm F1.4 Nikkor lens and 75-205mm F3.8 Vivitar zoom lens (zoomed to 205mm). You will note that the plane of focus is past the cross hair target written with a sharpie on news print slanted 45 degrees away from the camera.

I have owned this camera since new. It has been serviced only twice, both by Midwest Camera. I have never attempted any macro work with this camera that would have certainly revealed any focus issues.

Is the amount of focus error revealed in the test shots normal? I doubt it, but I am asking. Does the camera need an adjustment? When firing the camera with the lens off, the viewing mirror appears to act normally and the focus screen appears to be seated properly. If adjustable, where on the camera would an adjustment be made?

Please let me know if it needs servicing and I will send it in.

Loren Sattler

 

[onre]

They may have assumed that you're using the markings on the lens for your test pictures, not the viewfinder image.

 

[MartinCrabtree]

See "slanted 45 degree" comment in original post.

Completely missed that. My apologies.

 

[mdarnton]

I think they were probably speaking with reference to moving the focus ring on the lens, relative to the actual distance, when, for instance, the lens doesn't say infinity when focused there. That adjustment on Nikon lenses, unlike other brands, is not adjustable. They set infinity focus on the lenses using shims, moving the lens in and out until it agrees with the focus ring. At least that's what the service center told me. Why that topic came up is another story. . .

You are more likely to notice misfocus an long distances, not with macro work. In macro a given degree of error might move the focus back a mm or two, but at 20 feet the same magnitude of error might move focus to 200 feet, instead. Much more obvious!

 

[Vilk]

fwiw, a few years ago i had intermittent focus problems with one of my F2 bodies, similar to what you're seeing. severely backfocusing a frame or two, then the rest of the roll ok. i think low winter temperatures had something to do with it. i had to take it to my repair guy three times until he finally figured out a fix. it was not the screen, it was not the lens, it was not the finder, it was not film flatness. never a problem later

 

[John Koehrer]

I think they were probably speaking with reference to moving the focus ring on the lens, relative to the actual distance, when, for instance, the lens doesn't say infinity when focused there. That adjustment on Nikon lenses, unlike other brands, is not adjustable. They set infinity focus on the lenses using shims, moving the lens in and out until it agrees with the focus ring. At least that's what the service center told me. Why that topic came up is another story. . .

You are more likely to notice misfocus an long distances, not with macro work. In macro a given degree of error might move the focus back a mm or two, but at 20 feet the same magnitude of error might move focus to 200 feet, instead. Much more obvious!

The OP has solved his problem but anyway......
Never seen a Nikkor with shims to adjust focus. There are two things that can be adjusted in the lens.
The infinity stop, which is usually slotted and the focusing ring itself. Either may have slipped over the years
changing how the lens focuses.

Focusing error will be much more evident at close distance not far. DOF will hide any error at "infinity" but not at three feet.