To Nikon F users: large black marks in prism finder

[pvg]

Hi. I have received a Nikon prism finder (i.e., non-metered) from a very reputable second hand camera shop that offers return privileges. The finder, externally, looks good but it has two low internal horizontal black marks in the same horizontal axis of the glass (each appears to be ~1 x 4-5 mm), in addition to multiple other, much smaller, black spots. The two long marks cannot be focused (i.e., they are not sharp regardless of any distance set in the lens --while the smaller ones look distinctively sharp). Does anybody have experience with this kind of defect (particularly the fuzzy marks)? Are the marks simply detached black paint that can be easily cleaned by a professional or something worse? I have the option to return the finder if this would not be something fixable at moderate cost. Thanks for any opinions.

 

[stupid leica]

this is a VERY common problem on standard prisms.
I believe if you look back at some of my earlier posts you'll find me inquiring about similar stuff.
Basically, the black paint/sealant on the prism flakes off. You can pull the cover off the prism (there are screws under the leather) and touch it up with a paint pen, sharpie, whatever- or there are probably more "professional" methods you could use.
I have done this on two prisms, BTW.

Is the eyepiece on this finder good? it is usually difficult to find a finder that has both a good prism and a good eyepiece (they are plagued with separation).

 

[Mackinaw]

I gather you see these marks when you look through the viewfinder. If so, what you are probably seeing are marks on the outside of the prism on the actual silver coating. I've seen this happen on other SLR's and is usually caused by glue or tape that has gradually degraded the silver. Best remedy is to find a new prism.

Jim B.

 

[pvg]

nikon finder with black marks

nikon finder with black marks

...Is the eyepiece on this finder good? it is usually difficult to find a finder that has both a good prism and a good eyepiece (they are plagued with separation).

Thanks Leica and Jim for your rapid responses. The outside of the viewfinder looks quite good and I did not see glass separation but it is very distracting for actual use as it has many black marks. At this point, I think it will be more simple just to return it.

Best,

PVG

 

[John Hermanson]

The prism (a solid block of glass) has foam rubber holding it down. The now-rotting foam has eaten through the paint/aluminum coating and can now be seen as you look through the finder. John

 

[stupid leica]

If it is a black prism, it can be very hard to find one in good external (and internal) shape for a reasonable price. If yours was a good price and the "only" problem is what you have described, i think it would be worth it to do the simple fix i mentioned above. That is what i did with my black F standard.

 

[Livesteamer]

So this suggests Nikon F prisms have the same rotting foam problem as OM1 cameras? Should good prisms be dismantled to clean out the rotten foam before it damages the prism? Joe

 

[dbarnes]

I think I read on Nikonians.com that the prisms in the F's metered finders are the same glass as in the unmetered finders, opening the door to prism transplants.