Fungus on K1000 Prism?

Tom Taylor · Jan 2, 2023

Pulled out my 2 K1000 bodies yesterday and found this on the SE model:

It was also on the non-SE model but only just beginning at the lower section of the view finder. Both have been closet-stored together in a Pentax camera bag with a normal lens attached. Both lenses were clear as was the mirror and visible side of the focusing screen as seen when the lens is removed. Could it be that fungus avoided the lens, mirror, and screen but found a home on the prism or is there something else at play here?

M-88 · Jan 2, 2023

It looks like disintegration of prism silvering, not fungus.

Usually happens because of disintegration of prism foam damper, which then eats through the silvering. If so, it is not related to fungus.

Tom Taylor · Jan 2, 2023

Is that an easily (i.e., inexpensive) repairable situation? In the non-SE camera, a filament is just starting to appear at the very bottom of the viewfinder.

gone · Jan 2, 2023

Tom Taylor said:
Both have been closet-stored together in a Pentax camera bag with a normal lens attached.

Which would explain fungal growth. Cameras and lenses need air to breathe, just like us. Fungus will grow in a lots of different conditions, but that is an easy way to have it happen. If it is some crazy balsam deterioration. you'll need to replace the affected parts.

Not to make light of this because I know you're not at all happy w/ what you're seeing, but my upon first glance my first thought was, why are they photographing a close up shot from a grade Z monster movie?

Tom Taylor · Jan 2, 2023

I did a little googling and M-88 is apparently correct. It's not a balsam deterioration, in which case it would appear brownish, but disintegration of the prism silvering due to the deterioration of the damper. Here is what I found on the Pentax Forum:

Yes, that's de-silvering, sad to say.

Oddly enough, it's even more common in the K1000 - where they used a foam pad between the prism and the top cover. When the foam degrades it eats into the silvering. In the K1000, it's most often a vertical line down the prism's central divider.

In the Spotmatics, you get a horizontal line.

Read more at: https://www.pentaxforums.com/forums...desilvering-something-else.html#ixzz7pGxTL0Lo

While it has zero effect on negative quality, in my case it covers the split image focusing line on the SE and is just beginning on the other body. Repairing would entail replacing the prism and damper on one and possibly just the damper on the other - both of which is not economically feasible since I have replaced both bodies with F6's.

The issue came up yesterday when I mounted an 85mm Pentax f2.2 soft focus lens onto the F6 using a Fotodix Pro PK(a) to Nik -D Click Adapter. The split screen on the Nikon wouldn't line up -but came close. That's when I got the Pentax bodies out to check the lens. Due to de-silverling I couldn't see the focus line on the SX but on the other Pentax the mirco-focusing prism was sharp and view finder clearer. Looks like I am going to need a better adapter to use that lens on the F6.

M-88 · Jan 6, 2023

K1000 is a simple camera which would have been super cheap, if not the hype. So replacing its prism is a fairly simple DIY task as well, if one can find a donor prism.

Flange focal distance (distance from lens mount to film/sensor) of Pentax K mount is 45.46 mm, whereas same value on Nikon F mount is 46.50 mm. This makes it impossible to fit a lens adapter which would allow K-mount lenses focus to infinity on Nikon bodies, unless you employ an adapter with optical element. If your adapter has an optical element in it and yet it still doesn't focus to infinity, there's something wrong (You haven't specifically mentioned where it misfocuses - on infinity, or on closer objects, but I assume it's infinity). If the difference is not too dramatic, you could stop down the lens and hope to capture everything in focus thanks to deeper depth of field.

Please note: even if they allow infinity focus, these adapters with optical elements somewhat deteriorate image quality.

BobD · Jan 6, 2023

This is a common occurrence on the 5-screw K1000s

Andrew O'Neill · Jan 6, 2023

This de-silvering issue has been happening to some of our K1000's at my school.

AnselMortensen · Jan 6, 2023

Prism desilvering like that is also a common problem with non-metered Nikon F eyelevel prisms.

Kino · Jan 6, 2023

If you decide to go the rather "jankey" route of patching the prism with one of those spray-on mirror paints, just be aware that it does not reflect white light at the same color temperature as a typical prism.

I tried it on an Olympus OM1 prism before I found out that you can steal exact replacement prisms from the OM10; which I wound up doing instead.

The color temperature of white light this paint reflects is high, bluish around 6500 to 7000 degrees Kelvin.

At first I tried just cleaning off the lifting silver and painting that, but the effect was so unnerving, I went back and stripped the entire prism and painted it with the spray paint.

To me, it worked but was like looking through a permanent 80A color correction filter; perhaps not as strong, but pronounced.

In the end I took a junker OM10 and stole the prism; worked wonderfully.

I am not sure if there is a direct replacement from a similar model Pentax...

original2view · Jan 6, 2023

doesn't look like fungus

Helios 1984 · Jan 26, 2023

M-88 said:
K1000 is a simple camera which would have been super cheap, if not the hype. So replacing its prism is a fairly simple DIY task as well, if one can find a donor prism.

Flange focal distance (distance from lens mount to film/sensor) of Pentax K mount is 45.46 mm, whereas same value on Nikon F mount is 46.50 mm. This makes it impossible to fit a lens adapter which would allow K-mount lenses focus to infinity on Nikon bodies, unless you employ an adapter with optical element. If your adapter has an optical element in it and yet it still doesn't focus to infinity, there's something wrong (You haven't specifically mentioned where it misfocuses - on infinity, or on closer objects, but I assume it's infinity). If the difference is not too dramatic, you could stop down the lens and hope to capture everything in focus thanks to deeper depth of field.

Please note: even if they allow infinity focus, these adapters with optical elements somewhat deteriorate image quality.

Apparently, you can use the prism of a Canon Elan II >here<

gone · Jan 26, 2023

original2view said:
doesn't look like fungus

I agree, or at least it looks unlike any I have ever seen in or on a camera or lens. Kino's experience w/ just replacing the prism sounds good.

Is there a chance it's only an issue w/ the camera's viewfinder and not the prism? I had a Canon AV-1 that had a similar looking issue, and it was the viewfinder piece. Less expensive to replace, but you still had to take the top off the camera to do it. I decided it wasn't worth all the trouble and just sold it AS IS here w/ a bundle of other gear and bought another camera w/ the funds.

Kino · Jan 26, 2023

The early K1000 had foam under the hold-down strap on top of the prism. This foam decomposes, liquefies and runs onto the prism coating, eroding the mirror silver. It's not fungus, it's chemical damage lifting off the silver plating on the glass prism. No one I know of will strip and coat the prism for less than the cost of several used bodies, so it's not worth the effort.

If you do replace the prism, do NOT replace the foam. It's not really needed anyway, but you can put a thin cardboard shim under the hold-down strap if that makes you feel better.

Fungus on K1000 Prism?

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