Canon A1 issues - troubleshooting with pics included

[tuningsob]

Hello all, new to the site here. Recently acquired a Canon A1 and ran a roll of film through it only to find that my focus seemed to be off just slightly in the majority of shots. Found this odd so i ran a test using a tripod and cable release shooting at different apertures with 2 different lens (fd 50mm 1.8 and 24mm 2.8) both in manual and aperture priority mode. What i found was that on both in both manual and aperture priority mode and with both different lenses, when shooting wide open the subject is out of focus. This leads me to believe it is the camera and not the lenses. Does anyone have any ideas as to what could be the issue?


Test shots

 

[koraks]

Welcome to Photrio!

My first thought would be that there's a problem with the positioning of the ground glass or the mirror.

To check if it's the mirror: check if the plane of sharp focus moves backward or forward as you tilt the camera upwards and downwards. Since the mirror sits in the body at a slanted angle, the focus plane that you see in the viewfinder would move if the mirror is out of alignment.

I'm not familiar with the A1, but it might be worthwhile to verify if there are any ways in which the ground glass might become misaligned; perhaps there are even alignment screws underneath it?

 

[MattKing]

Welcome.
What koraks said!
The best way to test whether the focusing is matched between the viewing system and the film is to find something like a picket fence, and grab a longish tape measure. Set the camera up with the field of view looking along the fence line, with each picket a different distance away. Then take a movable marker of some sort and attach it sequentially to a picket that is a different distance away - say 2 feet away, 4 feet, 6 feet, 9 feet, 13 feet, 20 feet away, etc. At each distance, mark that distance on the marker, focus on it, and take a photo, using an aperture at or near wide open.
When you've developed the film, you will be able to determine if the viewing system's focus is front focusing, accurate or back focusing, and if that error is consistent.

 

[koraks]

For the more adventurous: what I do when testing focus of a 35mm camera is actually open the back and tape a piece of ground glass (or plastic) to the film gate so that it sits exactly where the film is. Then, with the back open and the mirror down, focus on a reference point. I usually take something around 3ft/1.5m from the camera as well as a reference point at infinity (or close to it) so I can verify both close and far focus. Flip the mirror up, for instance by making a bulb exposure and holding the shutter open (use a locking cable release) and with a loupe check the focus. If the reference point is not in focus, adjust focus on the lens to see which way you're off. In case of any deviations, systematically go through the optical path to identify possible causes and inspect these points in the camera closely.
This approach works well, but (1) sometimes takes some fiddling with the camera to coax it into having its shutter open and mirror up (if it's an SLR) for an extended period of time and (2) there is of course the inherent risk of damaging something when having everything open and exposed this way, so be careful and don't do this if you're unsure about the whole thing.

 

[Don_ih]

Your test shot for aperture priority of the 50mm lens wide open should match the one for manual - but the latter is much more in focus. Why did that focus change?

In the meantime, check that no crud got under the mirror. I can't remember if the focus screen is removable on the A1 - if it is, make sure it's fully engaged. I doubt it could be upside-down - nothing would be in focus.

There is always the possibility that someone cleaned dust off the mirror a little too aggressively and bent something in there. The mirror box, from what I can tell, is a replacement-only part.

 

[koraks]

Speaking of the mirror - doesn't the A-1 have foam dampers under the mirror's edges? I'd inspect those; they might have degraded over time and this might create alignment issues.

 

[Don_ih]

Speaking of the mirror - doesn't the A-1 have foam dampers under the mirror's edges? I'd inspect those; they might have degraded over time and this might create alignment issues.

I'm pretty sure there's just a metal post on the left side of the mirror box that supports the mirror in proper position.
The foam damper is at the top, for when the mirror goes up. That's either goo or already replaced or not there at all.

 

[tuningsob]

Wow, first of all thanks for all the responses, just joined this forum and its really cool to hear from everyone. Regarding the foam damper - yes there is one at the top that looks to be in great condition, possibly recently replaced even. These are all really great methods for testing and im going to try a few when I get a moment. I also have a great camera shop nearby so my last option would be to go for a CLA and have it looked at. This is my first electrical SLR and usually I shoot with something all manual and Pentax (K1000, MX) What I find strange is that focus issues only occur at the wide apertures, and clears up as I stop down. This happens on both lenses, if it was only on one lens id be inspecting that particular lens instead.

 

[MattKing]

Regarding the foam damper - yes there is one at the top that looks to be in great condition, possibly recently replaced even.

That is a clue - the screen may have been reinserted incorrectly.

What I find strange is that focus issues only occur at the wide apertures, and clears up as I stop down.

The issues are probably occurring at 1 stop down as well - just masked by the increased depth of field.
Unless those lenses have been seriously damaged you wouldn't be seeing focus shift from them.

 

[tuningsob]

That is a clue - the screen may have been reinserted incorrectly.

The issues are probably occurring at 1 stop down as well - just masked by the increased depth of field.
Unless those lenses have been seriously damaged you wouldn't be seeing focus shift from them.

Thats a good point, Ive included a couple pics of the focusing screen. Im unable to tell if its is placed correctly or not though unfortunately. Focusing Screen Pics Click Here

 

[Sirius Glass]

Hello all, new to the site here. Recently acquired a Canon A1 and ran a roll of film through it only to find that my focus seemed to be off just slightly in the majority of shots. Found this odd so i ran a test using a tripod and cable release shooting at different apertures with 2 different lens (fd 50mm 1.8 and 24mm 2.8) both in manual and aperture priority mode. What i found was that on both in both manual and aperture priority mode and with both different lenses, when shooting wide open the subject is out of focus. This leads me to believe it is the camera and not the lenses. Does anyone have any ideas as to what could be the issue?


Test shots

Welcome to APUG Photrio!!​

 

[tuningsob]

Update - after doing further research and some tests, it appears the focusing screen on this A1 is installed upside down. Everything I have read has indicated that the "shiny' side of the focusing screen should be facing down towards the mirror, and the matte should be facing up. Does anyone have experience on this and could verify?

 

[LimeyKeith]

From the Canon Service Manual: Hope this helps.

 

[gone]

it appears the focusing screen on this A1 is installed upside down. Everything I have read has indicated that the "shiny' side of the focusing screen should be facing down towards the mirror

In every camera I've owned, the shiny side goes toward the viewer, the matte (etched) side towards the lens or mirror. But that may not be true for your particular camera for some strange reason. Here's a thread from someone w/ an identical issue w/ your model camera. Pretty confusing.

My guess would be that the etched side of the screen "should" go towards the mirror/lens to get accurate focus, and since your's isn't, and since it has focus issues........

focusing screen

<p>On a Canon A-1, which side of the focusing screen should face the mirror? I understand that one is a glossy or polished surface and the other is a laser etched or matte surface.</p> <p>Thanks.</p>

www.photo.net

 

[Don_ih]

It should be virtually impossible to put the screen in upside down. But it might not be seated properly.

 

[tuningsob]

In every camera I've owned, the shiny side goes toward the viewer, the matte (etched) side towards the lens or mirror. But that may not be true for your particular camera for some strange reason. Here's a thread from someone w/ an identical issue w/ your model camera. Pretty confusing.

My guess would be that the etched side of the screen "should" go towards the mirror/lens to get accurate focus, and since your's isn't, and since it has focus issues........

focusing screen

<p>On a Canon A-1, which side of the focusing screen should face the mirror? I understand that one is a glossy or polished surface and the other is a laser etched or matte surface.</p> <p>Thanks.</p>

www.photo.net

Pretty confusing is right haha. From what i gathered from that thread the A series canons have the shiny side down while the F1 had the matte side down. Apparently this has something to do with the waist level veiwfinder that can be veiwed from the top on the F1s. My k1000 has the shiny side down. Dropping off at the local camera shop today, lets all hope its an easy fix because the rest of the camera appears to be in magnificent shape.