Lens won't focus to infinity?

FishyFish

FishyFish

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I bought a Ricoh KR-10 Super with Rikenon 50mm f/2 lens last week. Everything seemed fine, it's in nice condition (especially after a clean), but today I've noticed that the lens doesn't seem to focus to infinity. I estimate it focusses ok up to about 20 feet and then it's out. I did check the focus when I bought it, but obviously on things that were closer than infinity. :)

Any suggestions as to the problem and what I can do to fix it? If it's a lens alignment problem, will this mean the focus is out at all distances (even though it looks in focus through the viewfinder), or will it still be ok to use for closer subjects?

The camera only cost me a tenner, so it's not really worth me paying for a fix, but if it's likely to be a lens problem, I can look into buying another k-mount lens as a replacement.

Thanks.
 
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How do you know it won't focus to infinity? Just curious as to whether it's out when viewed at the film plane (or on the film) or whether the focusing screen could be misaligned. The same question applies as to how you know it's correct at closer distances.
 
StephenM said:
How do you know it won't focus to infinity? Just curious as to whether it's out when viewed at the film plane (or on the film) or whether the focusing screen could be misaligned. The same question applies as to how you know it's correct at closer distances.
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I don't know whether it does or not to be honest. I've not run a film through it yet so all I have to go on is the fact that the split prism won't focus on more distant objects. Likewise, although the viewfinder is telling me that it's focused on close objects, without seeing any results I don't know if it's accurate.
 
Buy another PK lens to test.

Shouldn't cost you too much and you've still got a good lens for your next camera (pk fit obviously)

I had a Ricoh XR-X back in the day.

Those Rikenon lenses are damn good.
 
Don't rely on the split image centre. Use your eyes and the plain part of the ground glass. Or, if there is a ring of micro-prisms around the split-image centre, use that.

Focus screens can get moved, even those intended to be fixed, so a test film is the only certain test.
 
john.margetts said:
Don't rely on the split image centre. Use your eyes and the plain part of the ground glass. Or, if there is a ring of micro-prisms around the split-image centre, use that.

Focus screens can get moved, even those intended to be fixed, so a test film is the only certain test.
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Thanks John. The micro prism ring doesn't get sharp either. I might try and find another lens to test it with.
 
john.margetts said:
Don't rely on the split image centre. Use your eyes and the plain part of the ground glass. Or, if there is a ring of micro-prisms around the split-image centre, use that.

Focus screens can get moved, even those intended to be fixed, so a test film is the only certain test.
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WHS
 
I had this with a Canon 70-200 lens, sent it to Canon and they repaired it for free, the guy I contacted at Canon knew what the fault was but I can't for the life of me remember what it was.
 
At the last resort you can adjust the lens for infinity.
 
The only way to know for sure without burning through multiple rolls of film is to rig up a temporary ground glass across the film gate with the rear door open. You can use simple opaque sellotape and stick a few pieces across the film gate (opening behind the shutter) then lock the camera in bulb using a locking remote release. Once you've got that setup, ideally on a tripod, place a few high contrast items at known distances away from the camera and focus on them using the viewfinder. Once they look in focus, check the distance mark on the lens to see if it matches and check the rigged ground glass to see if that's in focus too.

Assuming they all match, you don't have a problem with the lens :0). If the image isn't focused at the film gate but looks sharp in the viewfinder you've possibly got a loose/misaligned mirror.
 
stevelmx5 said:
The only way to know for sure without burning through multiple rolls of film is to rig up a temporary ground glass across the film gate with the rear door open. You can use simple opaque sellotape and stick a few pieces across the film gate (opening behind the shutter) then lock the camera in bulb using a locking remote release. Once you've got that setup, ideally on a tripod, place a few high contrast items at known distances away from the camera and focus on them using the viewfinder. Once they look in focus, check the distance mark on the lens to see if it matches and check the rigged ground glass to see if that's in focus too.

Assuming they all match, you don't have a problem with the lens :0). If the image isn't focused at the film gate but looks sharp in the viewfinder you've possibly got a loose/misaligned mirror.
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Thanks. When you say opaque sellotape, do you just mean the standard stuff, or the Scotch Tape type?
 
stevelmx5 said:
The Matt finish Scotch tape would work or even a piece of tracing paper if your scene was bright enough.
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I've done this using ordinary tissue paper ......such as loo roll.......if it's 3 ply, seperate them so you have just the one thickness.
 
FishyFish said:
Well, I got another lens for the camera only to find the problem persists, so I'm assuming the focussing screen is out of alignment. I guess I could try and fix it with some shims, but I think I'll just cut my losses and sell the two lenses (and maybe the body as a fixer-upper, although I doubt it's worth much).
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Well you will only know if you put a film in the camera...take a few shots with the lens at infinity and another focussing with the sharpest view.....no need to waste the rest of the film as you wind back and put it in another 35mm camera.
 
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