Canon P rangefinder prism polish

[shawn]

I picked up a Canon P that is in very nice shape, shutter looks like it is firing at all speeds well, minimal shutter wrinkling and the viewfinder was clear. But the rangefinder patch was very dim and difficult to see. Looking through the rangefinder window (or with a light shining through) it looked very hazy. Ended up pulling the top cover to inspect it and was assuming I'd have a small front surface mirror to clean. Turns out it doesn't use a mirror but a prism. The face of the prism facing the viewfinder was very dirty and it wouldn't clean up with any lens cleaner. Either whatever was on it was too tough for lens cleaner or it was very lightly etched from contaminants or earlier mold. 3 set screws and 1 screw holding a cover lets the prism come right out.

Used 1.5 micron glass polishing compound on a q tip to work on the face of the prism a little and it cleaned up very well.

Reassembled (those 3 tiny set screws are a pain) and recalibrated the rangefinder horizontally and vertically. The second image is dramatically better and it is easy to focus with both eyes open now. Also removed the old grease from the rewind knob (it was very heavy) and did a general cleanup.

Shawn

 

[santino]

Congrats! Looks good - another camera saved.

 

[Retro-Grouch]

You're a brave man! This isn't something I would even dream of undertaking. Your bravery has been rewarded with success.... this time!

 

[ranger9]

Great job! I'm guessing the glass itself was attacked by some environmental contaminant, and polishing was the only way to save it.

 

[shawn]

You're a brave man! This isn't something I would even dream of undertaking. Your bravery has been rewarded with success.... this time!

That polish is awesome, very fine and slow acting. I've used it to save a number of lenses and it hasn't let me down yet.

Shawn

 

[hanskerensky]

Good tip, thanks for sharing !

 

[bluesun267]

If the P is like the VI-L, VT, L1, VL (and variations) there was originally a deep blue anti-reflective coating on the front of the prism. Almost every one of these camera has a marred front coating to some degree (from prior cleaning mostly). Canon really used a weak, thin coating on these prisms, unlike their lenses of the same period. Usually it's not an issue, perhaps there's a small loss of contrast. In this case it is good to know there's a way to salvage a really bad one!

 

[hap]

That polish is awesome, very fine and slow acting. I've used it to save a number of lenses and it hasn't let me down yet.

Shawn

How do you actually "polish" a lens with that stuff. Is there a pattern based process or just what?