Mamiya M645 1000S with plain prism - rattles

As stated, I have a Mamiya M645 1000S with plain prism I just got from Roberts Camera that rattles after being attached to the body and was contemplating putting a thin strip of foam around the edge to remedy this annoying sound.

Any potential drawbacks?

I don't think this would have been acceptable when the camera was new, but I've never had a new M645.

I see no evidence of a spacer or foam strip missing on the body or prism; what gives?

BTW: I just got the used prism; I have had the body and a WL viewfinder for a while. It rattles too...

It's probably not totally dissimilar to the prism finder I have for my C330. I removed the bottom screws, and discovered some badly deteriorated foam in the prism roof. I had some foam tape 1/4" thick and put it in the top of the prism. When I put it back together, it was perfectly aligned. I'd marked the ground glass with a sharpy, so I had an index, and there weren't any non-vertical lines or pyramiding.

PS - After rereading your post, you may also have a somewhat loose attachment on the boy side, since it rattles regardless the finder.

I have a 1000s with multiple prisms and they all fit snugly. When attached, they can be forcefully moved horizontally by a tiny bit, but they do not rattle when the camera is shaken.

There is no foam on the camera body and the plain (non-metering) prism only has a small strip of foam (20x3mm) next to the eyepiece, as well as slightly protruding round rubber bumpers left and right of the glass, covering some screws. The metering prisms (PD-S/AE) also have foam (40x5mm) in the front, between the glass and the aperture coupling mechanism. The waist level finder only has the bumpers and no foam at all and still is a tight fit.

Adding foam yourself shouldn't hurt. I'd start with a small piece in the center or next to the glass, no need to cover all the edges. Also check that the screws for the hooks to which the prism attaches on the camera are well tightened.

PS. My plain prism suffers from strong mirror corrosion, which is caused by degrading foam inside the prism. The plain prism seem to be affected more by this than the other (possibly newer) prism types. So if your prism is clean then you should call yourself lucky and keep using it!

Cloudy 8 said:

PS. My plain prism suffers from strong mirror corrosion, which is caused by degrading foam inside the prism. The plain prism seem to be affected more by this than the other (possibly newer) prism types. So if your prism is clean then you should call yourself lucky and keep using it!

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Thanks for the observations! I added a small sliver of foam in the center and that seemed to do the trick. No screws were loose; who knows?

My prism has the requisite horizontal line through it and very, very slight corrosion starting, so I'll probably take it apart and clean out the old foam before it progresses anymore.

Been tempted to try to re silver a prism myself with silver nitrate using several methods found online. Maybe I'll buy a real cheap metered prism with horrible corrosion and give it a try...

Kino said:

Thanks for the observations! I added a small sliver of foam in the center and that seemed to do the trick. No screws were loose; who knows?

My prism has the requisite horizontal line through it and very, very slight corrosion starting, so I'll probably take it apart and clean out the old foam before it progresses anymore.

Been tempted to try to re silver a prism myself with silver nitrate using several methods found online. Maybe I'll buy a real cheap metered prism with horrible corrosion and give it a try...

Click to expand...

I think the line you speak of is actual deterioration of mirror surface (the mirror coating that is) at least that s what I saw somewhere on the web. Not sure if that is always he case with these symptoms though.

Witold said:

I think the line you speak of is actual deterioration of mirror surface (the mirror coating that is) at least that s what I saw somewhere on the web. Not sure if that is always he case with these symptoms though.

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Probably is... From what I can tell, the foam was adhered to the prism with a strip of mylar or foil with adhesive and the adhesive eats off the mirror silver.

The line doesn't bother me as much as the foggy delamination that eventually happens under the width of the adhesive strip.

Kino said:

Probably is... From what I can tell, the foam was adhered to the prism with a strip of mylar or foil with adhesive and the adhesive eats off the mirror silver.

The line doesn't bother me as much as the foggy delamination that eventually happens under the width of the adhesive strip.

Click to expand...

Sadly, this is a common problem with these. Saw one guy swapping in his otherwise working metered prism with a prism taken out from a non working one. Damage was only in area of a tape applied to prism.