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07-07-2022, 01:58 PM   #1
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Autofucus calibration of lens

I have a SMC Pentax-FA 1:1.7 50mm lens which shows a serious AF-error on several Pentax AF (including K1) camera bodies.When focused at infinity it focuses somewhere betwen 25-30 meters. Only when I set the focus adhustment in the camera at -10 the error is compensated.
I don't know what is causing the error, but more importantly: is there a way to re-calibrate the lens to get it focusing correctly?.

07-07-2022, 02:09 PM - 1 Like   #2
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QuoteOriginally posted by huge10 Quote
I have a SMC Pentax-FA 1:1.7 50mm lens which shows a serious AF-error on several Pentax AF (including K1) camera bodies.When focused at infinity it focuses somewhere betwen 25-30 meters. Only when I set the focus adhustment in the camera at -10 the error is compensated.
I don't know what is causing the error, but more importantly: is there a way to re-calibrate the lens to get it focusing correctly?.
What’s wrong with setting it to -10? The error is within tolerance. You can send a body and lenses for calibration but this may cause future headaches if the new lenses are different in their needs.
07-07-2022, 08:55 PM   #3
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I agree with UncleVanya, that is what the focus adjustment in the camera is there for. The camera should remember the lens and adjustment and revert to that every time it is on the camera, just forget about the adjustment and enjoy a fantastic nifty 50.
07-08-2022, 03:50 AM   #4
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It is an old lens so it could be wear or that something had become unaligned, or it needs CLA. Or possibly it has been like this since new.

But as others has said, I doubt it is worth the cost of sending it in for adjustment as long as the in camera compensation is enough.

Is it a lens you have had for a long time and it has gotten worse with time, or is it a lens you purchased used recently?

07-08-2022, 03:55 AM   #5
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QuoteOriginally posted by Fogel70 Quote
It is an old lens so it could be wear or that something had become unaligned, or it needs CLA. Or possibly it has been like this since new.

But as others has said, I doubt it is worth the cost of sending it in for adjustment as long as the in camera compensation is enough.

Is it a lens you have had for a long time and it has gotten worse with time, or is it a lens you purchased used recently?
I just got the lens and noticed the focusing offset.I have no other Pentax lens that has this to such extend. I'm just curious toknow how such lens would be calibrated. Is it through software (altering numbers in the lens) or through hardware?
07-08-2022, 04:32 AM   #6
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I think it can be both.

A service center can calibrate AF in software in the lens and/or camera if necessary.

But it may also be a hardware problem that has to be fixed first. If something have become unaligned, or if something is loose the focus error may change with time, or differ too much at different focus distances.
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