Nikon FM focus issue

[skylight1b]

I bought a Nikon FM from Blue Moon back in August and gave it to someone as a gift. The two rolls she put through it both had focusing issues. The focus was always slightly in front of where she actually focused. She told me this after the first roll, but I let her use a different lens for the next roll to make sure that wasn't the culprit. It was still off focus, so I assumed the mirror or prism was misaligned. I sent it to Blue Moon as part of their warranty and they could not replicate the issue. So after months later, I got it back and took the camera to use it with my most consistent lens. I have never had issues focusing in the past, yet the roll I put through it has the same issue still. I don't know where to go from here aside from buying her a new camera. I would like to have this fixed though. Anyone experience this? Anyone know who could actually repair it?

Example image from the most recent roll - You can see the focus is right at the bottom of the frame but I focused on the middle stairs.

 

[koraks]

This looks like a problem where the lens is not perpendicular to the film plane judging by how the focal plane tilts backwards (see bottom left corner). It seems the lens is tilted forward (edit: it may be swung to the right as well). In addition to this, there may also be a mirror/ground glass alignment problem at play.

 

[skylight1b]

This looks like a problem where the lens is not perpendicular to the film plane judging by how the focal plane tilts backwards (see bottom left corner). It seems the lens is tilted forward (edit: it may be swung to the right as well). In addition to this, there may also be a mirror/ground glass alignment problem at play.

You might be on to something there. I just looked for a good example of an angled focus plane and I definitely found one. The dogs head was chosen as the focus point.

 

[koraks]

Yeah, that's not good. This shot is clearer; it looks like the lens is angled to the right, and contrary to what I said before, it may be looking very slightly upward, not pointing down.

I'd start by inspecting the lens mount to see if it has sustained any damage, and whether it's installed properly.

It's conceivable this camera suffered a major accident that bent the frame out of alignment.

 

[skylight1b]

Yeah, that's not good. This shot is clearer; it looks like the lens is angled to the right, and contrary to what I said before, it may be looking very slightly upward, not pointing down.

I'd start by inspecting the lens mount to see if it has sustained any damage, and whether it's installed properly.

It's conceivable this camera suffered a major accident that bent the frame out of alignment.

The camera is nearly pristine. I really don't understand what could have happened, and now I'm beyond the warranty window.

 

[Chuck1]

You could use it for pinholes.

 

[koraks]

The camera is nearly pristine.

If it somehow sustained a blow to the lens that was mounted, it's conceivable that the damage was only visible on the lens.

In any case, I'd poke around the lens mount a bit to see what you can find there. That, and maybe have a look at the pressure plate to see if it functions properly.

 

[skylight1b]

If it somehow sustained a blow to the lens that was mounted, it's conceivable that the damage was only visible on the lens.

In any case, I'd poke around the lens mount a bit to see what you can find there. That, and maybe have a look at the pressure plate to see if it functions properly.

As far as I can tell, everything looks fine, but I don't know that I have a trained enough eye for that. I just want to be rid of this thing and start over.

 

[Nicholas Lindan]

My vote is mirror alignment.

First check for any evidence of amateur repair with damage to any screw heads. Check for evidence in any screw heads visible through the lens opening with the mirror moved out of the way. If screw heads are damaged then send the camera back with a note pointing out the damage.

To check just what is going on:

• Tape a page of the newspaper (if anyone remembers what one is...) to the wall and make a "+" in the middle to focus on;
• Put the camera on a tripod and set the height so the center of the lens is at the 'X';
• Move back a few feet to a comfortable shooting distance and at a horizontal 45 degree angle to the wall and focus on, and center, the "+";
• Take pictures with the lens wide open.

The results of this test will give you ammunition for returning the camera for replacement / refund if something is screwy.

If the focus is consistent (it is equally out of focus in either direction) up and down and side to side the problem is not lens perpendicularity. In any case, if the lens was not perpendicular, the focused on spot would be in focus in the picture. A non-perpendicular lens is sort of the norm if shooting with a view camera and it effects the plane of sharpest focus but not the focus point.

If the sharp->fuzzy transition points are equally distant from the "+" then there isn't (or shouldn't be) a focusing issue. In this case draw a pentagram on the floor, light candles at its five points and dance around the pentagram while waving a rubber chicken overhead to resolve the issue.

If the focus is to one side or the other of the X then the lens->focus screen and lens->film distances are different. If the focus is different top to bottom then lens perpendicularity can be suspect.

As the FM has a fixed focus screen, the screen position isn't likely to be the problem. Though if someone has gone in and mucked with things then bets are off. Is the screen the original pattern for an FM?

That leaves the only other possible issue as the mirror position. Is there any gunk on the back of the mirror? Is there any evidence of work on the inside of the mirror box?

Mirror alignment can shift if something goes haywire and the mirror doesn't return all the way. With the mirror down, does the lip of the mirror move if you press down on it? If so, return the camera with a note.

Cameras are sold for a reason - and one reason is that the camera isn't working quite right. A glaring malfunction is an obvious sale killer but something non-obvious can be a reason for someone selling a camera and walking away from it.

 

[koraks]

My vote is mirror alignment.

How does that explain the Scheimpflug movement to the focal plane?

 

[Nicholas Lindan]

How does that explain the Scheimpflug movement to the focal plane?

I don't see any. That's the reason for doing a controlled test and proving what is going on to any and all.

With all the Scheimpflug in the world, even with the film perpendicular to the lens, the focused on spot doesn't change.

 

[koraks]

I don't see any.

 

[Nicholas Lindan]

<Picture of poodle>

That's the picture where I don't see any.

If perpendicularity were the problem, and the focus point is the tip of the dog's nose, then the nose should be in focus. As to any tilt to the focus plane, from that confused and three dimensional subject, I'm afraid I can draw no conclusions except with regards to the aforesaid nose.*

I'm afraid we are just going to have to agree to disagree.

* Though I suppose the photographer may have been focusing on the lashes of the dog's closest eye.

 

[koraks]

That's the picture where I don't see any.

Odd.
So the one in the OP, how do you explain the extreme focus falloff towards the top while the building all along the bottom edge of the frame appears in focus. This can only happen if the focal plane is tilted.

Not sure if you regularly work with a view camera, but I think it's kind of obvious really.

Mind you, I think there's *also* an alignment problem.

 

[Nicholas Lindan]

Not sure if you regularly work with a view camera, but I think it's kind of obvious really.

I work with one very regularly: Sinar P & F, Shen Hao 8x10, Seneca 5x7, Speed Graphic (well, it's kinda half a view camera). Have been for 40 years. Lots longer if including University.

Though, damned if I can see any reason that I need to justify myself.

And, I'd say an ad hominum post is worthy of the intervention of a moderator.

 

[logan2z]

Anyone know who could actually repair it?

I recently used Dean's Camera Repair in Southern California to repair a Nikon FT-3 that nobody else would touch. The repair wasn't cheap, but the camera came back working perfectly and Dean was a pleasure to work with. I'm sure he could repair whatever is ailing your FM.

Dean's Camera Repair
(310) 782-8619

 

[koraks]

And, I'd say an ad hominum post is worthy of the intervention of a moderator

Don't take it that way; it wasn't intended as such. I'm just puzzled you don't see it, that's all.

 

[Nicholas Lindan]

Don't take it that way; it wasn't intended as such. I'm just puzzled you don't see it, that's all.

You are right. I think I read your post in the wrong way.

As to why two people don't see eye to eye. Well, that's politics, isn't it... À chacun son goût, De gustibus non est disputandum, and all that.

Sometimes agreeing to disagree is as good as it gets until new information becomes available.

 

[koraks]

That's OK. To be sure, I think your advice is sensible and OP should also check for an obvious mirror or ground glass alignment issue.

 

[ic-racer]

Assuming your camera has never been tampered, lenses, lensmounts, and fronts of cameras can be easily bent out of alignment. Almost every repair document explains how to check for such alignment problems when cameras come in for repair.

If the camera has ever been opened, then perhaps there was a failure of replacing shims or washers. Though I don't see any in the Nikon service manual for that camera.

Here is a good example. Zeiss 28mm f2. I honestly don't know how or when this got bent, just one day I went to use it and it looked like the Leaning Tower of Pisa.

I was able to bent the frame back. A little exciting due to floating elements and two helicoids.

Of course, as pointed out, the mirror and prism and finder will have no light passing through them when and exposure is made, so they are of no consequence here.

 

[MattKing]

Correct me if I'm wrong, but I don't see how problems with the mirror or the ground glass can affect whether the plane of focus is parallel with the film plane.
It could certainly affect whether the focus is at the right distance.

 

[RalphLambrecht]

My vote is mirror alignment.

First check for any evidence of amateur repair with damage to any screw heads. Check for evidence in any screw heads visible through the lens opening with the mirror moved out of the way. If screw heads are damaged then send the camera back with a note pointing out the damage.

To check just what is going on:

• Tape a page of the newspaper (if anyone remembers what one is...) to the wall and make a "+" in the middle to focus on;
• Put the camera on a tripod and set the height so the center of the lens is at the 'X';
• Move back a few feet to a comfortable shooting distance and at a horizontal 45 degree angle to the wall and focus on, and center, the "+";
• Take pictures with the lens wide open.

The results of this test will give you ammunition for returning the camera for replacement / refund if something is screwy.

If the focus is consistent (it is equally out of focus in either direction) up and down and side to side the problem is not lens perpendicularity. In any case, if the lens was not perpendicular, the focused on spot would be in focus in the picture. A non-perpendicular lens is sort of the norm if shooting with a view camera and it effects the plane of sharpest focus but not the focus point.

If the sharp->fuzzy transition points are equally distant from the "+" then there isn't (or shouldn't be) a focusing issue. In this case draw a pentagram on the floor, light candles at its five points and dance around the pentagram while waving a rubber chicken overhead to resolve the issue.

If the focus is to one side or the other of the X then the lens->focus screen and lens->film distances are different. If the focus is different top to bottom then lens perpendicularity can be suspect.

As the FM has a fixed focus screen, the screen position isn't likely to be the problem. Though if someone has gone in and mucked with things then bets are off. Is the screen the original pattern for an FM?

That leaves the only other possible issue as the mirror position. Is there any gunk on the back of the mirror? Is there any evidence of work on the inside of the mirror box?

Mirror alignment can shift if something goes haywire and the mirror doesn't return all the way. With the mirror down, does the lip of the mirror move if you press down on it? If so, return the camera with a note.

Cameras are sold for a reason - and one reason is that the camera isn't working quite right. A glaring malfunction is an obvious sale killer but something non-obvious can be a reason for someone selling a camera and walking away from it.

my vote is for fous screen misalignment.

 

[skylight1b]

So I got the go ahead to send it back again. I don't know if they'll find the problem now if they couldn't the first time, but it's worth a shot. In the meantime, if anyone knows someone selling a black FM that definitively works, I can at least make good on a failed present.

 

[Nicholas Lindan]

So I got the go ahead to send it back again.

Whaaaaat? After all this, you are going to leave the cause of the problem unresolved? All our good advice wasted, just wasted.

Probably the best thing to do, though.

But, is Blue Moon going to load the camera with film, take shots of a test target, develop the film and make an enlarged print (or, I suppose make a scan, sigh) to judge the issue?

 

[skylight1b]

Whaaaaat? After all this, you are going to leave the cause of the problem unresolved? All our good advice wasted, just wasted.

Probably the best thing to do, though.

But, is Blue Moon going to load the camera with film, take shots of a test target, develop the film and make an enlarged print (or, I suppose make a scan, sigh) to judge the issue?

I know I know...

I don't think I have the eye to figure this out. All the suggestions make sense, but everything looks fine to me. I'd rather someone else dismantle it. I wish I knew what they did to test it the first time, but I feel like a roll of film was not involved. Hopefully they'll try that now.