Nikon FM focus issue

[koraks]

is Blue Moon going to load the camera with film

In cases like these, I prefer to out the camera on a tripod, open the back and visually inspect the projected image on the film plane with a piece of ground glass. A final check after repairs would have to be done with film, but the ground glass approach makes a repair effort much quicker.

 

[Ian C]

In the photo of post #3, nothing appears critically focused as I view it. There seems to be a focus disparity among scene elements at approximately the SAME distance from the lens? Note the extreme and abrupt focus difference between the head and tail of the dog. These appear not much different in distance from the lens. Even if this had been shot with a fast lens at a fully opened aperture, the apparent focus difference due to shallow depth of field wouldn’t look like that.

This makes me wonder about the flatness of the film. I’d check the function of the pressure plate. It must hold the film flat and in register against the film rails above and below the opening to the shutter.

If this is a pressure plate problem, it wouldn’t be seen through the viewfinder. It would be useful to state both the lens and the aperture setting used.

 

[skylight1b]

In the photo of post #3, nothing appears critically focused as I view it. There seems to be a focus disparity among scene elements at approximately the SAME distance from the lens? Note the extreme and abrupt focus difference between the head and tail of the dog. These appear not much different in distance from the lens. Even if this had been shot with a fast lens at a fully opened aperture, the apparent focus difference due to shallow depth of field wouldn’t look like that.

This makes me wonder about the flatness of the film. I’d check the function of the pressure plate. It must hold the film flat and in register against the film rails above and below the opening to the shutter.

If this is a pressure plate problem, it wouldn’t be seen through the viewfinder. It would be useful to state both the lens and the aperture setting used.

I have been thinking about the pressure plate, and it might explain their difficulty replicating the problem if they have been focused (no pun intended) on the mirror or prism. For this photo specifically, I know it was a 55mm micro f/2.8 lens, likely at f/5.6, but I'm not 100% sure of the aperture.

 

[Ian Grant]

In cases like these, I prefer to out the camera on a tripod, open the back and visually inspect the projected image on the film plane with a piece of ground glass. A final check after repairs would have to be done with film, but the ground glass approach makes a repair effort much quicker.

That has to be the first check after inspecting the pressure plate to see that's it's functioning properly. It is possible the bayonet mount (on the body) is out of alignment.

Ian

 

[250swb]

The mirror or prism alignment only affects what you think you are seeing, not the actual photograph which is the lens projecting light onto the film. The mirror cannot distort the image, especially because it is out of the way when the exposure is made. So it's either the pressure plate, lens mount, or lens. Of those it's easy to check the body, which I assume the OP has done, so my guess would be the lens and perhaps an element has shifted or not been seated properly if its been cleaned.

We don't even know the type of lens the OP was using and some aftermarket zooms can be pretty awful out of the box, and shooting wide open exaggerates the problems.

 

[skylight1b]

The mirror or prism alignment only affects what you think you are seeing, not the actual photograph which is the lens projecting light onto the film. The mirror cannot distort the image, especially because it is out of the way when the exposure is made. So it's either the pressure plate, lens mount, or lens. Of those it's easy to check the body, which I assume the OP has done, so my guess would be the lens and perhaps an element has shifted or not been seated properly if its been cleaned.

We don't even know the type of lens the OP was using and some aftermarket zooms can be pretty awful out of the box, and shooting wide open exaggerates the problems.

Just to note, across 3 different rolls of film, 4 different lenses were tried, all of which work fine (great actually) with another FM and FM2. I'm leaning toward a pressure plate issue at this point.

 

[MattKing]

Just to note, across 3 different rolls of film, 4 different lenses were tried, all of which work fine (great actually) with another FM and FM2. I'm leaning toward a pressure plate issue at this point.

Or perhaps a bent frame and resulting displacement of film rails.
Which would imply serious impact damage to the camera body!

 

[bernard_L]

The film gate rails define the film plane. The pressure plate just needs to be present and... press the film; but no critical alignment for that component.

 

[MattKing]

The film gate rails define the film plane. The pressure plate just needs to be present and... press the film; but no critical alignment for that component.

This is correct, although a malfunction in the film transport and pressure plate might result in the film moving away from the plane set by the rails.

 

[250swb]

The pressure plate would have to be massively out of kilter and clearly visible just by looking at it, but the OP says they have looked at it so it can't be that. If however the film had been bunched up by somebody turning the film rewind crank the wrong way for a long time and without any understanding of what that does it could be maybe possibly to bunch the film up enough to put a counter acting pressure on the pressure plate and force it up.

But you know, you give a camera to a friend and then try to report on problems without any actual hands on experience and it's a crap shoot as to the cause.

 

[Nicholas Lindan]

But you know, you give a camera to a friend and then try to report on problems without any actual hands on experience and it's a crap shoot as to the cause.

But that's what makes it all interesting/entertaining/enraging.

As to facts - we don' need no steenkin' facts, dey jus confuse t'ings.