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07-04-2022, 08:17 AM   #1
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Dust stuck in my pentax k1000 viewfinder?

I just got this camera secondhand and there is a large black dust-like obstruction in my viewfinder that I didn't notice : (. I am wondering if this is easily fixable and what kind of cost I am looking at for the repair? It looks like a particle from black foam.

Any help would be greatly appreciated.

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07-04-2022, 08:31 AM - 1 Like   #2
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Prism is desilvering. You would need to get a new prism. Good thing is that it won't affect your pictures.
07-04-2022, 08:45 AM   #3
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As mentioned that is not dust. That is prism desilvering which means the prism is loosing the reflective silver coating. Practically not repairable. I've been experimenting on this with very limited success. Prism would need to be replaced. While annoying it will not show in the pictures. But keep in mind the meter is reading light from the prism. If it grows it may eventually affect the meter readings. That problem is common on last gen K1000 from China, the one with plastic top and bottom.

Thanks,
Ismael
07-04-2022, 10:52 AM   #4
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QuoteOriginally posted by ismaelg Quote
As mentioned that is not dust. That is prism desilvering which means the prism is loosing the reflective silver coating. Practically not repairable. I've been experimenting on this with very limited success. Prism would need to be replaced. While annoying it will not show in the pictures. But keep in mind the meter is reading light from the prism. If it grows it may eventually affect the meter readings. That problem is common on last gen K1000 from China, the one with plastic top and bottom.

Thanks,
Ismael
Hi, thank you so much for such a fast reply. Can I ask if you know what causes prism desilvering to happen and how to avoid it?

07-04-2022, 12:49 PM - 3 Likes   #5
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Hello,

The pentaprism is a solid (and beautiful) chunk of glass. All but two surfaces are internal mirrors. In order to achieve that, a microscopically thin and even layer of silver is deposited in the desired surfaces. Since it is very delicate, it is usually covered with a black protective paint.
Here you can see the pentaprism removed from an earlier Pentax H3, but the concept is the same.


Desilvering is when that coat of silver gets damaged on the surface. It is no longer a mirror. A common cause is deteriorating foam solvents eating into the top coat and then into the silver itself.
I'm guessing your K1000 is a late generation Made in China. Desilvering is a common issue especially over the top ridge of the prism, which is where you are seeing your problem (in the middle of the image from top to bottom).
I suspect it is a combination of quality of materials and quality of the silvering process. Cost cutting measures were already at full swing when production was moved from Hong Kong to China around 1990.
The only thing you can do short of replacing the prism is to make sure the area is clean of old foam. But you need to be very careful because if you try to clean the prism you risk the possibility of even more irreversible damage.
The permanent solution would be to resilver the prism but I have yet to find anyone to do that commercially, as I suspect it is not practical from a business standpoint.
Hope this helps.

Thanks,
Ismael
07-04-2022, 10:21 PM   #6
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The Chinese K1000 cameras have tape on the top of the prism. Something in the adhesive makes the prism de-silver. Nothing can stop it from happening and it can't be affordably be repaired. Like Ismael, I have tried a number of things with little success.
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