Is there anyone who can repair my Nikon FM2 focus issue?

rpavich · Nov 2, 2017

I'm wondering if there is an independent person who would and could tackle my focus issue with my Nikon FM2.
I bought this camera from Robert's camera and I believe that from the start it was back or front focusing, I forget which but it was about 1" off or so.
I had a camera shop repair it but after two tries it's still not good enough, they say it's "in spec" but I have two FM2's and I can tell the difference.

Before I toss it, is there anyone who would tackle it for a nominal fee?

David Lyga · Nov 2, 2017

The true, accurate focus is determined by the precise level that results from what the front of the mirror rests upon. Some cameras have a simple set screw, others have a rather crude metal length which the bottom of the mirror rests upon. Still others have a more complex arrangement. VERY small mirror height differences make a lot of difference with focus.

But, the bottom line is this: If the REAL (film plane) focus is closer than APPARENT (viewfinder) focus, lower the mirror. If the REAL (film plane) focus is further than APPARENT (viewfinder) focus, raise the mirror.

You want to discover what I mean? Focus as accurately as you can with a lens of narrow depth of field (telephoto or large aperture normal lens) at a stationary subject. NOTE THE EXACT LOCATION ON THE LENS BARREL. Then, gently raise the front of the mirror and place a tiny piece of index card between where the front of the mirror rests and that post it rests upon. This raises the mirror ever so slightly. Then ... focus on the same subject, carefully. I promise that that initial location on the lens barrel will now be quite different.

With all cameras that I buy I do this precise test and do not quit until the VG focus is precisely what the film plane designates. Too many simply 'trust' VF focus to be accurate.

"Tossing" an FM2 would be one of the most stupid things you ever did. - David Lyga

rpavich · Nov 2, 2017

David Lyga said:
The true, accurate focus is determined by the precise level that results from what the front of the mirror rests upon. Some cameras have a simple set screw, others have a rather crude metal length which the bottom of the mirror rests upon. Still others have a more complex arrangement. VERY small mirror height differences make a lot of difference with focus.

But, the bottom line is this: If the REAL (film plane) focus is closer than APPARENT (viewfinder) focus, lower the mirror. If the REAL (film plane) focus is further than APPARENT (viewfinder) focus, raise the mirror.

You want to discover what I mean? Focus as accurately as you can with a lens of narrow depth of field (telephoto or large aperture normal lens) at a stationary subject. NOTE THE EXACT LOCATION ON THE LENS BARREL. Then, gently raise the front of the mirror and place a tiny piece of index card between where the front of the mirror rests and that post it rests upon. This raises the mirror ever so slightly. Then ... focus on the same subject, carefully. I promise that that initial location on the lens barrel will now be quite different.

With all cameras that I buy I do this precise test and do not quit until the VG focus is precisely what the film plane designates. Too many simply 'trust' VF focus to be accurate. - David Lyga

Well isn't that interesting!
I'll take that task and see what happens. That would tell me what has to be adjusted I believe.

David Lyga · Nov 2, 2017

Do the test and determine whether that damn mirror needs to be ever so slightly raised or lowered. Too many do not know this but the concept is utterly simple.

Test with tiny pieces of film on the film plane and develop them to determine film plane focus. Make certain that this film is totally upon the film gate: Otherwise you will not get film plane focus and increase your problems! - David Lyga

rpavich · Nov 2, 2017

David Lyga said:
Do the test and determine whether that damn mirror needs to be ever so slightly raised or lowered. Too many do not know this but the concept is utterly simple. - David Lyga

Thank you very much for this info! it would be awesome to shoot this camera again, it was my first FM2 and it's brassed up and gorgeous!

rpavich · Nov 2, 2017

Ok...now that I've given this some thought...I'm wondering; how will I know what the film plane focus IS?
I'll know that shimming the mirror changes the apparent focus...right? But how will I know when the actual focus is achieved?

edited to add...I see that you just answered this. Thanks.

David Lyga · Nov 2, 2017

Please call it 'REAL' focus, not 'actual' : it makes it easier to talk about without changing the vernacular. REAL focus is achieved ONLY by inspection of the negative. NO OTHER WAY.

REAL FOCUS (come on, R, use the brain) is determined with inspection of that negative. Choose a stationary object like a picket fence which will show exactly what is in REAL focus (when film is developed) and be able to repeat the precise distance you are from it. Now, focus on a precise spot. that is the APPARENT focus because you THINK that that is in focus. Mark it on both the object and lens barrel. Now develop that neg and see how close you are to what you THOUGHT was in focus. How far on that picket fence is the real focus from that apparent focus? NOW you are able to truly see what needs to be done with that mirror. You have to measure the difference between both APPARENT (VF) focus with REAL (film plane) focus.

Again, the brain R: Once you have the REAL focus you now know what the apparent focus has to be. You raise or lower that mirror until the APPARENT focus precisely matches the REAL focus. The film plane is the ONLY determinate of precise focus: it is what is the truth, nothing less.

To make this simpler, you don't have to find an actual picket fence. I use the rear of an LP album with bold printing and hold it 45 degrees from the camera, set upon a table.But my distance from that album is always utterly precise. 35mm development did not come out of sloppiness. Ask Oskar Barnack.

And, in payment for this I demand that you send me a dozen FM2 cameras, postpaid, posthaste. - David Lyga

rpavich · Nov 2, 2017

David Lyga said:
Please call it 'REAL' focus, not 'actual' : it makes it easier to talk about without changing the vernacular. REAL focus is achieved ONLY by inspection of the negative. NO OTHER WAY.

REAL FOCUS (come on, R, use the brain) is determined with inspection of that negative. Choose a stationary object like a picket fence which will show exactly what is in REAL focus (when film is developed) and be able to repeat the precise distance you are from it. Now, focus on a precise spot. that is the APPARENT focus because you THINK that that is in focus. Mark it on both the object and lens barrel. Now develop that neg and see how close you are to what you THOUGHT was in focus. How far on that picket fence is the real focus from that apparent focus? NOW you are able to truly see what needs to be done with that mirror. You have to measure the difference between both APPARENT (VF) focus with REAL (film plane) focus.

Again, the brain R: Once you have the REAL focus you now know what the apparent focus has to be. You raise or lower that mirror until the REAL focus precisely matches the APPARENT focus. The film plane is the ONLY determinate of precise focus: it is what is the truth, nothing less.

To make this simpler, you don't have to find an actual picket fence. I use the rear of an LP album with bold printing and hold it 45 degrees from the camera, set upon a table.But my distance from that album is always utterly precise. 35mm development did not come out of sloppiness. Ask Oskar Barnack. - David Lyga

Got it. thanks again.

David Lyga · Nov 2, 2017

Even the 'postpaid, posthaste' part? - David Lyga

shutterfinger · Nov 2, 2017

Film thickness for 135 format is .004 inch thick (4mil), TriX Pan, Fuji Super HQ.
Common size ground glass is inexpensive on ebay and can be cut down easily.
A piece of ground glass cut to fit onto the film guide rails, a piece of regular glass or clear acrylic cut to fit the guide rails then strips of Scotch Magic Transparent Tape placed next to each other without overlapping , placed over the film gate ( ground side or tape side facing the lens ), the shutter locked open on B with a locking cable release, will allow the operator to critically focus the lens at the film plane with a loupe then adjust the mirror to the film plane focus much faster.
Film can be and should be used as a final test. Larger formats allow the film thickness either side of the actual film plane to be acceptable but in 135 format I would prefer 1/2 of the film thickness or less for the ground side or tape side of the test ground glass position for mirror alignment.

Dan Fromm · Nov 2, 2017

Interesting discussion. OP, you say focus is off by 1". At what distance?

Very interesting that no one mentioned that the FM2 has an interchangeable focusing screen. Is the screen in right side up and properly seated?

rpavich · Nov 2, 2017

shutterfinger said:
Film thickness for 135 format is .004 inch thick (4mil), TriX Pan, Fuji Super HQ.
Common size ground glass is inexpensive on ebay and can be cut down easily.
A piece of ground glass cut to fit onto the film guide rails, a piece of regular glass or clear acrylic cut to fit the guide rails then strips of Scotch Magic Transparent Tape placed next to each other without overlapping , placed over the film gate ( ground side or tape side facing the lens ), the shutter locked open on B with a locking cable release, will allow the operator to critically focus the lens at the film plane with a loupe then adjust the mirror to the film plane focus much faster.
Film can be and should be used as a final test. Larger formats allow the film thickness either side of the actual film plane to be acceptable but in 135 format I would prefer 1/2 of the film thickness or less for the ground side or tape side of the test ground glass position for mirror alignment.

Thank you for filling in the details, i have a weekend project I can see.

rpavich · Nov 2, 2017

Dan Fromm said:
Interesting discussion. OP, you say focus is off by 1". At what distance?

Very interesting that no one mentioned that the FM2 has an interchangeable focusing screen. Is the screen in right side up and properly seated?

Yes, that’s the first thing I checked

BrianVS · Nov 2, 2017

To check actual focus with my Nikon and Contax rangefinder cameras, I use a blank strip of exposed film and tape it into the film chamber. (I have some special tools for testing a Leica) I use a 15x loupe that has a glass reticle to hold the negative against the rails. Then I focus with the rangefinder, and inspect the image on the film. Testing an SLR would be similar. Set the shutter to "B", or "T" if the camera has that setting. Some interchangeable focus screens come with thin shims for the final adjustment, but the film cameras did not. Adjustment was via the mirror. If the camera is suffering from back-focus, the path to the focus screen is too long. You have to move the optics in closer to focus on the screen than is required to focus at the image plane of the camera. In this case- shimming the focus screen would work.

E. von Hoegh · Nov 3, 2017

Since angle of incidence = angle of reflection, the correct position for the mirror is precisely 45 degrees to the lens' axis (45 + 45 = 90) regardless of whether this setting gives correct focus on the screen; correcting focus by moving the mirror can introduce other errors, and will lose the (possibly correct) original setting. The ideal procedure is : verify flange distance from and parallelism to the filmplane, verify correct angle and position of mirror, move screen in or out to make focus on screen coincide with focus on filmplane.

rpavich · Nov 3, 2017

E. von Hoegh said:
Since angle of incidence = angle of reflection, the correct position for the mirror is precisely 45 degrees to the lens' axis (45 + 45 = 90) regardless of whether this setting gives correct focus on the screen; correcting focus by moving the mirror can introduce other errors, and will lose the (possibly correct) original setting. The ideal procedure is : verify flange distance from and parallelism to the filmplane, verify correct angle and position of mirror, move screen in or out to make focus on screen coincide with focus on filmplane.

Ahhh....that makes a lot of sense!
I'll check that out.

E. von Hoegh · Nov 3, 2017

rpavich said:
Ahhh....that makes a lot of sense!
I'll check that out.

Translated, it means "don't move the mirror until you have eliminated every other possible cause"

rpavich · Nov 3, 2017

E. von Hoegh said:
Translated, it means "don't move the mirror until you have eliminated every other possible cause"

That's what I took it to mean.

BrianVS · Nov 3, 2017

Just one thought- have you tried swapping the focus screens between the known good camera and the one that is off? These screens are old, the screen itself might not be sitting correctly in the frame. Could be the frame or the screen. Worth a try.

rpavich · Nov 3, 2017

BrianVS said:
Just one thought- have you tried swapping the focus screens between the known good camera and the one that is off? These screens are old, the screen itself might not be sitting correctly in the frame. Could be the frame or the screen. Worth a try.

Yes, that was the first thing I tried as I assumed that the mirror wasn't seated correctly or that something was wrong with it.

BrianVS · Nov 3, 2017

Kim Coxon posted my old instructions for shimming a J-3. It has pictures of the Canon 7 with a film strip and the 15x loupe that I use.

http://www.pentax-manuals.com/repairs/j3service.pdf

That's probably the next step that I would take if it were me. Would also be a good way to determine if the focus was even across the frame, if the mirror was not at the correct angle.

rpavich · Nov 3, 2017

BrianVS said:
Kim Coxon posted my old instructions for shimming a J-3. It has pictures of the Canon 7 with a film strip and the 15x loupe that I use.

http://www.pentax-manuals.com/repairs/j3service.pdf

That's probably the next step that I would take if it were me. Would also be a good way to determine if the focus was even across the frame, if the mirror was not at the correct angle.

Oh thanks. I'll check it out.

BrianVS · Nov 3, 2017

"Long Shots" but I've seen it: re-attached mirror where glue used changes the alignment, ie mirror is too far out. Film not sitting in the proper location due to some slight dent in the pressure plate. I've recemented a mirror on a Vivitar SLR and changed out the pressure plate on a Nikon F3 before. All it takes is about 0.1mm to knock the focus of a 50mm lens off by 1inch at 3feet.

shutterfinger · Nov 3, 2017

Download the F2 factory service manual at http://arcticwolfs.net/ and verify all is at spec.
(you're in for a workout )

E. von Hoegh · Nov 3, 2017

shutterfinger said:
Download the F2 factory service manual at http://arcticwolfs.net/ and verify all is at spec.
(you're in for a workout )

A workout indeed! The OP has an FM-2.

Is there anyone who can repair my Nikon FM2 focus issue?

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