Should I get a new pressure plate?

[Certain Exposures]

Last night I was changing rolls and I noticed my pressure plate is developing a slight impression of a film negative. I am not sure how long it has been there. It was not always there. That much is certain.

I assume that wouldn’t ever get deep enough to make a noticeable impact on film flatness, right?

 

[ChrisGalway]

For an f/8 aperture, a diffraction-limited lens has a depth of focus of around +/- 64 microns (f-number squared). For f/4, it would be around +/-16 microns ... but it's unlikely that any lens would be diffraction-limited at f/4, so the dof would be >16 microns for a real lens.

I'd be very surprised if this "impression" you describe is deep enough to have any effect. The eye is remarkably sensitive to very small surface changes, if you get the illumination just right.

 

[MattKing]

Have you seen this about Garry Winogrand's M4? (scroll down)
https://cameraquest.com/LeicaM4G.htm

 

[AnselMortensen]

I had that same issue arise with the Nikon FE2 that I bought new in 1985 and ran a gazillion rolls through before it finally gave up.
Nothing to worry about.

 

[Kodachromeguy]

Have you seen this about Garry Winogrand's M4? (scroll down)
https://cameraquest.com/LeicaM4G.htm

On Winogrand's camera, the strap eyelets have almost worn through. One day, one will break through and the camera will crash to the ground.

 

[koraks]

a slight impression of a film negative

An impression or a shadow?
Either way - no. I'd focus on important things instead.

 

[awty]

Clean the plate.
Unlikely film will be abrasive enough to wear a groove into metal.
Film will leave a residual on the plate, especially if left in the camera for a extended time, like in the Winogrand camera.

 

[Don_ih]

Clean the plate.
Unlikely film will be abrasive enough to wear a groove into metal.
Film will leave a residual on the plate, especially if left in the camera for a extended time, like in the Winogrand camera.

That's right. The impression on Winogrand's camera was likely made by dirt from his fingers getting on the film. If it was made by friction of film sliding against the pressure plate, you wouldn't be seeing sprocket holes.

If you want to see a genuinely worn pressure plate, look here.

 

[Certain Exposures]

Thanks, everyone! I learned a few new things.

I suspect it could be dirt based on the chat about Winogrand's camera. I will double-check when I finish the roll.

 

[awty]

That's right. The impression on Winogrand's camera was likely made by dirt from his fingers getting on the film. If it was made by friction of film sliding against the pressure plate, you wouldn't be seeing sprocket holes.

View attachment 426475

If you want to see a genuinely worn pressure plate, look here.

Looks like someone attacked it with a rasp.

 

[Don_ih]

Looks like someone attacked it with a rasp.

I should've taken a picture when I had the camera apart. All the paint is worn off where the sprocket holes travel. The vertical scratches are probably from loading the film (where the cut part ends) - none of those scratches are deep enough to feel.

I think it must've seen a lot of film over its 90 years. I've got an older one (with the collimation hole in it) that has no scratches at all.

 

[reddesert]

My feeling about marks on the plate, like in Winogrand's camera, is that they are probably due to a chemical reaction between the film base, or contaminants on the film base like finger oil, and the surface finish of the pressure plate (paint or plating).

I don't think they are friction scratches because as others said, there are no sliding marks. But I also am not sure why several people think it's from dirt. What's the mechanism? Is it that there's dirt on the film base and it gets pressed into the plate? Why doesn't that leave sliding marks?

Anyway, I don't think any of these pressure plates need replacement, even Winogrand's. The marks are probably something like only several microns in depth, and the film base has some structural bending stiffness, so it doesn't follow the plate exactly. The unevenness in the surface of the film is probably unmeasurable and certainly less than the depth of focus. There are better things to worry about, like rangefinder adjustment, technique, and so on.

 

[Don_ih]

But I also am not sure why several people think it's from dirt.

Finger oil is dirt when it's not on a finger. ... its own finger.

 

[TheFlyingCamera]

Unless the springs behind the pressure plate are failing, any loss of thickness where the film passes over is unlikely to cause a loss of critical focus. Of course, if you're really concerned about it, get a Contax RTS III with the ceramic pressure plate and film plane vacuum. If the weight of the RTS III is too much, get an ST with the ceramic pressure plate, minus the vacuum.

 

[Don_ih]

Or an old M3 with glass plate.

 

[Certain Exposures]

Thanks, everyone! I learned a few new things.

I suspect it could be dirt based on the chat about Winogrand's camera. I will double-check when I finish the roll.

That's right. The impression on Winogrand's camera was likely made by dirt from his fingers getting on the film. If it was made by friction of film sliding against the pressure plate, you wouldn't be seeing sprocket holes.

View attachment 426475

If you want to see a genuinely worn pressure plate, look here.

I should've taken a picture when I had the camera apart. All the paint is worn off where the sprocket holes travel. The vertical scratches are probably from loading the film (where the cut part ends) - none of those scratches are deep enough to feel.

I think it must've seen a lot of film over its 90 years. I've got an older one (with the collimation hole in it) that has no scratches at all.

I just checked and it is not dirt. It is hard to show on camera, though.

I believe the baseplate is going to end up with the same wear pattern Don showed in his link. The black is wearing down where the sprocket holes travel and the baseplate has matching scratches lengthwise (that cannot be felt).

Since you all say it will not harm my negatives I have no concerns. Thank you.

 

[Certain Exposures]

I had that same issue arise with the Nikon FE2 that I bought new in 1985 and ran a gazillion rolls through before it finally gave up.
Nothing to worry about.

How did your FE2 pass? Was it your only camera for many years?