Canon P viewfinder cleaning

cptrios · Jun 24, 2021

Hi all,

I recently got a Canon P from a Japanese eBay seller. As described, it's not in great shape, but seems functional (though the self-timer lever spins around freely, unconnected to anything internal, again as described). What wasn't in the description is what appears to be some fungus somewhere in the viewfinder. It's only visible when the light hits it at certain angles, so my utterly uneducated guess is that it's on a mirrored surface or part of a prism.

There do seem to be several resources on dismantling the camera, but I'm just wondering if anyone has any specific advice on how I might clean off the glass elements in the viewfinder/rangefinder without damaging anything (I'm particularly worried about the mirror finish). Would the usual ammonia/peroxide blend kill any fungus without causing an issue?

(Before anyone asks, a return isn't really an option. Between September and March, I returned five reasonably expensive cameras bought on eBay, all with good reason and after perfectly friendly communication with sellers. But that must have flagged my account, and it got suspended! I was able to get it reinstated after somehow managing to talk to a human being, but at this point I'm terrified of returning anything else. Thankfully, at the already low price and after a partial refund by the seller, I'm only out around $75 on the camera, which I consider a totally acceptable cost for a "project.")

4season · Jun 24, 2021

Here's what I do: I fold / roll / tear a sheet of lens tissue such that I wind up with a couple of floppy "brushes" with fuzzy tips. Moisten with a drop cleaning agent of your choice and proceed. The trick is that the rather limp tube limits the amount of pressure you can exert on anything. Try it out first on something you can risk damaging, but with a bit of practice, you ought to be able to clean pretty much anything including front-silvered mirrors and silvered frame line indicators. I use ordinary lens cleaning fluid for most work, and sometimes resort to an alcohol-based sensor cleaner if I think I'm dealing with greasy residue.

Couple of other areas to be aware of: Cement holding the rangefinder window in place may be weak, ditto with windows for frame counter and so on. Check and re-cement as needed. RF windows often have some black painted borders which are easily damaged, so plan accordingly and don't be surprised if you need to do some touch-up work.

Fungus shouldn't be much of a problem if you keep your cameras clean and watch that humidity: I think storage conditions around 55% relative humidity or less ought to minimize chances of fungus.

cptrios · Jun 24, 2021

4season said:
Here's what I do: I fold / roll / tear a sheet of lens tissue such that I wind up with a couple of floppy "brushes" with fuzzy tips. Moisten with a drop cleaning agent of your choice and proceed. The trick is that the rather limp tube limits the amount of pressure you can exert on anything. Try it out first on something you can risk damaging, but with a bit of practice, you ought to be able to clean pretty much anything including front-silvered mirrors and silvered frame line indicators. I use ordinary lens cleaning fluid for most work, and sometimes resort to an alcohol-based sensor cleaner if I think I'm dealing with greasy residue.

Couple of other areas to be aware of: Cement holding the rangefinder window in place may be weak, ditto with windows for frame counter and so on. Check and re-cement as needed. RF windows often have some black painted borders which are easily damaged, so plan accordingly and don't be surprised if you need to do some touch-up work.

Fungus shouldn't be much of a problem if you keep your cameras clean and watch that humidity: I think storage conditions around 55% relative humidity or less ought to minimize chances of fungus.

Thanks! That's really useful! If I do have to re-cement anything, which should I use to do so?

cmacd123 · Jun 24, 2021

do be careful - some of the half silvered mirrors in that class of camera can lose their silvering if touched in any way.

4season · Jun 24, 2021

cptrios said:
Thanks! That's really useful! If I do have to re-cement anything, which should I use to do so?

I got this product recommendation from the Aki-Asahi web site:
https://www.cemedine.co.jp/global/en/technology/elastic/superx/index.html
To date, have only used the gray-colored stuff, but actually, clear would be easier to deal with for most camera repairs. Not like working with Pliobond, it's not solvent-based, cures slowly, and is only moderately sticky until it does. It seems to remain pliable over time, and excess can be cleaned with naptha. I've ordered small tubes of the stuff from Japanese sellers.

cptrios · Jun 24, 2021

cmacd123 said:
do be careful - some of the half silvered mirrors in that class of camera can lose their silvering if touched in any way.

This is something that definitely worries me. Would it make sense to just submerge components in cleaning solution without any wiping at all? I'm only really interested in making sure the fungus is dead - if it's still visible, it's no biggie. With any luck, it'll be on a non-mirrored element.

cptrios · Jun 24, 2021

4season said:
I got this product recommendation from the Aki-Asahi web site:
https://www.cemedine.co.jp/global/en/technology/elastic/superx/index.html
To date, have only used the gray-colored stuff, but actually, clear would be easier to deal with for most camera repairs. Not like working with Pliobond, it's not solvent-based, cures slowly, and is only moderately sticky until it does. It seems to remain pliable over time, and excess can be cleaned with naptha. I've ordered small tubes of the stuff from Japanese sellers.

This might be a stupid question, but are naphtha and lighter fluid essentially interchangeable?

4season · Jun 24, 2021

cptrios said:
This might be a stupid question, but are naphtha and lighter fluid essentially interchangeable?

In this context, yes, lighter fluid is fine.

BTW, I don't know that I'd try too hard to "disinfect" the camera, because I'm pretty sure that fungus spores are everywhere, so it's mostly a matter of cleaning up existing growth and taking steps to prevent future outbreaks, and fungus tends to thrive in warmth and humidity.

reddesert · Jun 24, 2021

I would just try to clean the other surfaces and leave the half silvered mirror alone. The risk/reward ratio is too great with the half silvered mirror.

If you want to make sure you don't get any more fungus, exposure to sunlight and then storing the camera someplace dry is probably good enough. I've never felt the need to use special disinfectants on a lens, alcohol is enough for lens cleaning, ammonia and peroxide are more reactive than I want to use.

awty · Jun 24, 2021

Ive pulled a few apart. Most surfaces can be cleaned with out going too deep once you have removed the top plate. The problem is with the prism splitter as it is sealed, you can take it out easy enough (although I have had one that was glued down and wouldn't budge)and clean the out side, but if it has fungus or deterioration in side there is nothing you can do. Having said that simply cleaning everything you can get to will greatly improve the optics. You need to be careful with the contrast patch mirror for the range finder, don't use alcohol just a damp cotton bud will do.

awty · Jun 24, 2021

Here's one where a I removed the prism. Once that is removed you can get to everything else. The P might be slightly different.

cptrios · Jun 25, 2021

awty said:
Ive pulled a few apart. Most surfaces can be cleaned with out going too deep once you have removed the top plate. The problem is with the prism splitter as it is sealed, you can take it out easy enough (although I have had one that was glued down and wouldn't budge)and clean the out side, but if it has fungus or deterioration in side there is nothing you can do. Having said that simply cleaning everything you can get to will greatly improve the optics. You need to be careful with the contrast patch mirror for the range finder, don't use alcohol just a damp cotton bud will do.

First of all, thanks for these posts! I'm always really encouraged by how helpful people on here can be.

I took a screenshot from this Youtube video, which seems pretty useful.

It seems like there's 1. A plastic lens that appears more or less safe to clean, 2. The front prism, and 3. A glass unit that can't be separated and could definitely have fungus inside. The author of the video cleans the outside of 1 and 2, but isn't shown cleaning any other part. Does anyone know which faces of the three pieces I should NOT touch? Or will they be pretty obviously mirrored if/when I take my own camera apart?

awty · Jun 25, 2021

cptrios said:
First of all, thanks for these posts! I'm always really encouraged by how helpful people on here can be.

I took a screenshot from this Youtube video, which seems pretty useful.
View attachment 278377
It seems like there's 1. A plastic lens that appears more or less safe to clean, 2. The front prism, and 3. A glass unit that can't be separated and could definitely have fungus inside. The author of the video cleans the outside of 1 and 2, but isn't shown cleaning any other part. Does anyone know which faces of the three pieces I should NOT touch? Or will they be pretty obviously mirrored if/when I take my own camera apart?

No. 2 has a bracket with two screws holding down the bracket. Once the bracket is removed the prism should come out with a little nudge. I have had one that was fixed in and wouldnt move, so dont push too hard. Once out it is easy to clean the outside. Also makes it easy to get to No. 1 and clean. You cant clean inside of prism.
Im not sure how hard it is to take out the box between the eye view window No.1 and the Prism No.2 so you will need to make your own decision on that. If it comes out easy you may not need to take out the prism no.2 to clean.
There is a little mirror in the little box inside the range finder window that can be cleaned by moistened cotton wool bud.

cptrios · Jun 26, 2021

Ok, I'm gonna shoot a roll just to make sure it's alright mechanically, then I'll take a crack at cleaning. VF is perfectly usable as-is, thankfully!

awty · Jun 26, 2021

cptrios said:
Ok, I'm gonna shoot a roll just to make sure it's alright mechanically, then I'll take a crack at cleaning. VF is perfectly usable as-is, thankfully!

Yes its not a hard job to clean the optics, I have 4 of the models previous to the P and all had dingy view finders till I cleaned them, even with a small amount of fungus or deterioration in the prism they are still all bright and contrasty enough. The timer might just be a loose screw under the plate. Adjusting the vertical and horizontal focus is easy to. Never had any major problem with them mechanically, occasionally the frame lines aren't always equal which is pretty common for 60 year old cameras

mbl73 · Jun 10, 2023

I just cleaned a Canon P and thought I'd share my experience. It might be interesting for some. When you open the bracket to take out the prism you will find that there is a thin glass glued on one side of the prism (the side that faces to the front of the camera). In my case it was easy to remove with just a little bit of pressure of my finger nail. The old glue made my viewfinder hazy especially in the corners. The thin piece of glass was easy to clean. A thin layer of glue was still on the prism, but I got it removed with a blade very carefully. I didn't want to glue it back to the surface of the prism, so I decided to try a tiny drop of glycerine between prism and glass and bingo. Enough to connect it slightly to the prism and then hold it with the bracket. The viewfinder was amazingly clear afterwards, I'd say as clear as in my Canon 7. This was a very nice improvement.

Dan Daniel · Jun 10, 2023

mbl73 said:
I didn't want to glue it back to the surface of the prism, so I decided to try a tiny drop of glycerine between prism and glass and bingo. Enough to connect it slightly to the prism and then hold it with the bracket. The viewfinder was amazingly clear afterwards, I'd say as clear as in my Canon 7. This was a very nice improvement.

Interesting. Thanks for putting this out there. How will this hold up over time? I don't know much about glycerine. Will it flow down and out or is surface tension enough to keep it in place? And will it evaporate over time, and if so what time frame?

mbl73 · Jun 11, 2023

That's something to follow up. I pressed out almost all of it before I put the prism back. There isn't much left between glass and prisma, so I assume surface tension will be sufficient to keep it in place.

cptrios · Jun 12, 2023

Dan Daniel said:
Interesting. Thanks for putting this out there. How will this hold up over time? I don't know much about glycerine. Will it flow down and out or is surface tension enough to keep it in place? And will it evaporate over time, and if so what time frame?

I suspect that much depends on whether or not the days are allowed to go by.

(Sorry, couldn't help it.)

Canon P viewfinder cleaning

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