Canon AE1-P aperture control not working correctly

Craigus

Craigus

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Following my other thread ( https://www.talkphotography.co.uk/threads/central-stripe-out-of-focus-update.647451/ ) trying to get to the bottom of an issue with my Canon AE1 Program, I've been having a look at the lens and camera this evening and I seem to have found an issue with the camera that could potentially be to blame... hard to explain so please bear with me.

In short, it appears that when the shutter is fired the lens is only stopping down momentarily when the sutter is first pressed. For instance, if I take the lens off the camera and fire the shutter in bulb mode, I see the little lever move that stops the lens down but it doesn't stay there as I hold open the shutter, which it should for the duration of the exposure, rather it flicks across so fast you can barely see it when first pressed then returns. DOF preview is not working either, and I know the way it works on an AE1-P is a bit odd having to reset it and wind the film on etc, but it is not working at all.

Is this something anyone knows about with this camera, or is it a common issue with certain cameras etc? Do you think it could be to blame for the results in the other thread?
 
Thanks for the link ken, I followed a few further ones and it seems there is something not right with the two levers that control the aperture. Will be sending it off to Miles Whitehead I think for a repair soon.
 
Craigus said:
Following my other thread ( https://www.talkphotography.co.uk/threads/central-stripe-out-of-focus-update.647451/ ) trying to get to the bottom of an issue with my Canon AE1 Program, I've been having a look at the lens and camera this evening and I seem to have found an issue with the camera that could potentially be to blame... hard to explain so please bear with me.

In short, it appears that when the shutter is fired the lens is only stopping down momentarily when the sutter is first pressed. For instance, if I take the lens off the camera and fire the shutter in bulb mode, I see the little lever move that stops the lens down but it doesn't stay there as I hold open the shutter, which it should for the duration of the exposure, rather it flicks across so fast you can barely see it when first pressed then returns. DOF preview is not working either, and I know the way it works on an AE1-P is a bit odd having to reset it and wind the film on etc, but it is not working at all.

Is this something anyone knows about with this camera, or is it a common issue with certain cameras etc? Do you think it could be to blame for the results in the other thread?
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You didn't say with the camera on "B" and the lens stopped down .....does the lens stay stopped down until the shutter button is released...also with the back open and pointing the camera at a bright light should give you a rough idea if the lens is stopping down and the shutter speeds are working ok.
 
excalibur2 said:
You didn't say with the camera on "B" and the lens stopped down .....does the lens stay stopped down until the shutter button is released...also with the back open and pointing the camera at a bright light should give you a rough idea if the lens is stopping down and the shutter speeds are working ok.
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Shutter speeds are working fine but it is not stopping down the lens at any point at any speed or aperture or even in bulb mode.
 
Craigus said:
Shutter speeds are working fine but it is not stopping down the lens at any point at any speed or aperture or even in bulb mode.
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Well if it's the same with another lens then it looks like the camera needs a repair :(
Off camera with the Canon FD lenses you can see if the lens stops down (with a fiddle), but the newer FDn it's more difficult as the levers lock up.
 
Yeah there seems to be nothing wrong with the lens as it will stop down when off the camera. I have another cheap fd lens arriving today so will test with that one to confirm.

I think it is worth repairing as it's in good condition and the values only seem to be going in one direction at the moment.
 
Craigus said:
Yeah there seems to be nothing wrong with the lens as it will stop down when off the camera. I have another cheap fd lens arriving today so will test with that one to confirm.

I think it is worth repairing as it's in good condition and the values only seem to be going in one direction at the moment.
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So it would seem all your shots were with the lens wide open i.e. camera wasn't stopping down lens, which depending on the lens would give inferior results.
 
excalibur2 said:
So it would seem all your shots were with the lens wide open i.e. camera wasn't stopping down lens, which depending on the lens would give inferior results.
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That is the conclusion I came to, but that doesn't make sense as some of the shots I know were stopped down to f/8 or beyond in line with the meter (which does seem to be working okay) they would be hugely over-exposed if the exposure was actually shot 5 or 6 stops brighter, which they aren't.
 
When suspicious of aperture action you can see if it is fully closing by looking through shutter from the back. One of mine was giving over exposure only when using fast shutter speeds and on first few shots of a session. Seeting it to different speeds and f/16 could see that faster then 1/125th the aperture was not shutting all the way until after 5 or six shots so had do a bit of work on lens. Yours sounds a little different in that you suspect it is opening again too soon - same test works just looking at the lower speeds - but if exposure looks OK then at least you will get reassured. Not sure if this would link to the blurry middles though.
 
Craigus said:
That is the conclusion I came to, but that doesn't make sense as some of the shots I know were stopped down to f/8 or beyond in line with the meter (which does seem to be working okay) they would be hugely over-exposed if the exposure was actually shot 5 or 6 stops brighter, which they aren't.
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h'mm do the negs look ok as the labs can still scan and produce decent looking shots if over by up to 6 stops

http://petapixel.com/2015/08/10/how-much-can-you-overexpose-negative-film-have-a-look/
 
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