[jeryst]

I have been playing around with the autofocus adjustment on my K20D because the pictures just do not seem really sharp.
By using the adjustment, I have seen the sharpness improve dramatically, so I have a question.

Would this adjustment be different for each lens used, or is it a strictly internal camera function?

[JohnX]

Each lens.

Lenses and cameras are made to +/- tolerances. What the adjustment is allowing is you to match (or closely match) those tolerances.

Unfortunately you'll sometimes find lenses and cameras at the same (extreme) tolerance range, either + or - , in which case you might not be able to 'match' them.

That said, Pentax can do it for you, for a particular lens/camera combo, but that could result in all your other lenses being outside adjustment range.

This is also the reason some buyers will change lenses until they get what they regard as a 'good copy'.

You should also be aware that there is a so called 'hack', (it's not, but that's what will come up in a search), that enables the 'hidden' menus in the camera that are used by technicians, etc. One of the results is an improved , ie bigger, range of AF adjustments.

You'll find threads on here referring to the 'hack'.

[philbaum]

K20, K7, and K5 all allow global and individual lens AF fine adjustments. I'm not sure how many lenses can be individually adjusted and adjustments retained by the camera's memory. Its at least 10, maybe more on the later models.
The global adjustment allows plus or minus 10 adjustment and the individual lens adjustment also allows the same range.

If you program in a -10 global and a -10 individual lens, in theory, one could adjust -20 for any singal lens.

The camera remembers the individual lens adjustment when the lens have the Pentax identification coding built into the lens body. So that if you mount a different lens, the camera remembers the adjustment for that lens. This lens memory function of the camera body may not work well for some third party lenses because they don't have the necessary Pentax ID built into the lens. Sigma lenses sometimes fall into this category - i don't know the details on this issue.

I posted a recent link in the lens forum to an article by lensrental company about the "myth of soft lenses". Well worth the reading.

hope this helps

[JohnX]

If you program in a -10 global and a -10 individual lens, in theory, one could adjust -20 for any singal lens.

I thought it was global or individual, ie they're not cumulative?

[jeryst]

I know that on a manual lens you focus by eye, but what about using the cameras focus indicator when using a manual lens?

If the autofocus is incorrect, would the lens be out of focus when the indicator lights up?

If so, would the global adjustment be the one to use?