Focus adjustment

I've just bought a (used) Sigma 10-20mm and find it's back focusing, I've tried adjusting in camera but +/_ 10 is not enough, does anyone know what I can do?

It's worse at 20mm than 10mm but I can't get it spot on using 'focus adjustment' in camera

What body are you using and do your other lenses need a lot of adjustment?

I'm using the K5.
No, all other lenses are ok

I have the same combo and I have also found that the Sigma 10-20 sometimes causes the top LCD to scroll through the setting flashing numbers as it goes. I have found that making sure the lens is seated as far clockwise as possible assists the connections.

I doubt this is the case with you as it sounds as though the lens is acting normally apart from the back focus.

Silly question but have you tried cranking the adjustment both way full - and full + to see if it is responding in any respect?

Yes i've adjusted as much as possible and it makes a difference but the maximum of 10 is not enough

Only thing I can think of now is to make an adjustment set to all lenses as to make a base adjustment. This can be up to 10.

Then make a lens adjustment up to 10 for the Sigma. This, I think, will effectively give up an adjustment of up to 20.

The other lenses though would then need correcting by the base 10 if they were good to begin with.

Hope I'm making sense and not too sure if this would work.
Also a bit extreme....good luck.

The base adjustment would require the debug menu to be accessed. This allows a global adjustment for all lenses, but is only of any use if the camera is focussing wrongly to a similar extent with all lenses, like one of my K-x's used to do. If it's just the 10-20 that is significantly out, the only proper solution is to get the lens seen to, or ditch it and buy one that's right.

Regards
David

Hi David,

The K5 does have both adjustments available within the regular user interface without going to debug.

I'm probably with you though the best option is to have the lens looked at....cheers.

i think what David is saying is that it is either one or the other, you cannot have both in camera. you use a programme "PK Tether" to access debug mode and apply a global setting then either +or - as required. you do this with camera af adjust settings reset to zero before you start as you are in fact moving your start point + or - whatever you set in debug so if you set +10 you have moved your zero point +10 from what it was, THIS WILL BE APPLIED TO ALL LENSES. come out of debug and Pk Tether. if that does not cure it you can go into camera af adjust and adjust individual lenses if the "apply one" option is available and the camera recognises the lens.

others on here will probably know more about PK Tether and how to use it.

One of the reasons why I always buy Pentax.