Checking shutter bounce/slow curtain without wasting film (Canon P)

cptrios · Jul 11, 2021

Well, this is my second thread about this camera, after first wondering how to clean the VF. I've shot two rolls with it and there's clearly something up with the shutter - either curtain bounce or something similar. It's inconsistent shot-to-shot and I'm not even sure it always happens at the same speeds (though I didn't have the presence of mind to write down speeds for each shot). Here's what it looks like:

(I scanned this one with the opposite face down and didn't bother to reverse it)

I've found a few useful threads out there, including one that seems to be about this exact issue, but my question is; if I take a crack at fixing it, is there any way for me to know it's fixed without actually burning a roll of film? I did take the following slow-mo video (sadly my phone 'only' does 240fps) and interestingly don't see any bounce. So I don't know if that'll work.

By the way, if anyone wants to buy this thing and do it themselves before I dive in, let me know! I don't actually like the camera that much, so I'd probably be fixing it to sell anyway.

Sirius Glass · Jul 11, 2021

You have a shutter problem, not shutter bounce. Get a CLA to have it fixed properly and then get back to enjoying photography.

ic-racer · Jul 11, 2021

I was hoping to see a video of shutter bounce.

cptrios · Jul 11, 2021

Sirius Glass said:
You have a shutter problem, not shutter bounce. Get a CLA to have it fixed properly and then get back to enjoying photography.

Sigh, if that's the only route, I'll just sell it and take a hit. No more throwing good money after bad for me.

ic-racer said:
I was hoping to see a video of shutter bounce.

Well, I embedded a video of shutter something. Shutter what, I don't know!

Don_ih · Jul 11, 2021

At the very least, the camera will need to be disassembled down to where you can access the entire track the curtain follows, as well as any gears that might have bits of film in there. The curtain looks to be in pretty bad shape, also. If you're not comfortable with full disassembly, you should sell it.

gone · Jul 11, 2021

Unfortunately, this sort of problem crops up quite often in old cameras. Could be a light leak, could be shutter issues, or both. If you're not familiar w/ overhauling one of these cameras, best to send it off for a CLA or sell it. If it were me, I'd sell the Canon for what I could get and buy a Bessa R because those things are bullet proof. Great meters too.

reddesert · Jul 11, 2021

This camera uses steel curtains that are known for getting dimples but still working, so the "bad shape" is not necessarily a problem; it's not going to be full of pinholes like a deteriorated cloth shutter curtain.

OP, how much is your time worth? If you spend time repairing a camera, it's probably worth the cost of a cheap roll of B&W film to test it. The slow motion video doesn't reveal anything obviously wrong, so what I would do is run a roll through exposing at each of the speeds in order to figure out where it's happening. The other thing to do is to examine the negatives to see if the extra light bleeds outside the frame; if it does, then it's a light leak and not a shutter problem.

cptrios · Jul 11, 2021

Thanks for the responses everyone! I'm still pondering. I don't think a complete disassembly is beyond my abilities, but it'd be a first for me. I shall continue ruminating. And I'd love a Bessa R but I've got to sell a bit of stuff before thinking of investing in one...I have very strict ingoing-outgoing rules about photo gear!

reddesert said:
This camera uses steel curtains that are known for getting dimples but still working, so the "bad shape" is not necessarily a problem; it's not going to be full of pinholes like a deteriorated cloth shutter curtain.

OP, how much is your time worth? If you spend time repairing a camera, it's probably worth the cost of a cheap roll of B&W film to test it. The slow motion video doesn't reveal anything obviously wrong, so what I would do is run a roll through exposing at each of the speeds in order to figure out where it's happening. The other thing to do is to examine the negatives to see if the extra light bleeds outside the frame; if it does, then it's a light leak and not a shutter problem.

I thought of this, but the extent of "outside the frame" light bleeds is as you see in the 2nd and 3rd shots - just a smidge over the top and bottom edge of the frame. I suppose it could be coming from somewhere within the mount/shutter box?

Mamiya_Repair · Jul 11, 2021

The video shows an obvious shutter issue: the bar on the closing curtain is not clearing the aperture at the end. This will cause light to bleed through to the film.

Patrick Robert James · Jul 11, 2021

Check and see if the curtains stay together when you are winding the film/shutter. Looks like they don't by the negs. Wind it a little and see if there is any light leaking between them.

cptrios · Jul 11, 2021

Mamiya_Repair said:
The video shows an obvious shutter issue: the bar on the closing curtain is not clearing the aperture at the end. This will cause light to bleed through to the film.

Ah I was wondering about that. So this bit should be completely hidden when the shutter's not cocked?

Could that just be an obstruction, maybe?

cptrios · Jul 11, 2021

Patrick Robert James said:
Check and see if the curtains stay together when you are winding the film/shutter. Looks like they don't by the negs. Wind it a little and see if there is any light leaking between them.

The plot thickens! They do overlap when cocking the shutter, but they only start overlapping when the trigger is a click or two into its motion. Dunno why I didn't try shining a light in in this state before, but look at it when the shutter's uncocked!

I have to say; the temptation to open it up is rising.

John Koehrer · Jul 14, 2021

Quick & ugly fix would be to adjust the travel time on the closing curtain. BUT! Even exposure needs curtains
that run at the same speeds so it if/maybe it could be sorta kinda not be apparent.
The right way would having it cleaned, lubed & adjusted.

cptrios · Jul 23, 2021

Well, I fixed it! At least temporarily. Opened up the main case and couldn't see any blockages. Also noticed that the self-timer mechanism seems to be working but the lever isn't connecting (and my spanner isn't small enough to get it off).

Then I opened up the bottom and cleaned the mechanism with probably-not-enough lighter fluid. After a few shutter fires, the curtain closed all the way. Sadly I don't have any appropriate lubricant, so it was really more of a proof-of-concept thing. The second curtain is now back to not totally closing, so I'm guessing it needs a more thorough cleaning and some good oil. At least it's not busted!

nicholasnicholas · Aug 24, 2023

Did you get to the bottom of this? Mines doing the same!

cptrios · Aug 25, 2023

Sorry - I sold the camera rather than trying to fix it. Good luck with yours, though!

Checking shutter bounce/slow curtain without wasting film (Canon P)

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