Sigma 18-50 ex - problems! with focusing

Hi All Sage Ones,

I bought a Sigma 18-50 EX DG (do you ever wish they were just called Dave) from ebay for my K10. This is not the new macro version.

And on tests I keep getting a focus problem. The lens seems to be focusing behind the the subject.

Through the view finder it seems to focus and my shutter speeds are about 125 on a variety of apertures. Weirdly One shot was a 10th and came out sharp.

Is this a common problem! As I will need to get back onto the seller.

Thanks Ladies and Gents

Blue

PS This is the second ex lens that I haven't been Happy with. Shame the Pentax are always more expensive and rarer!!

Which camera?

The only reason I ask is that my K10D had consistent back-focus on all lenses
I see from your signature that you have the *ist-D - try it on that as well.

The wider the aperture, the more critical focus becomes!
There's some info here: https://www.pentaxuser.com/forum/viewtopic.php?t=6126

HTH!
Matt

cheers Matt (your pic scares me)

I will try on the istd as my k10 is the coupled camera at the moment.

shame - tonight I'm photographing a friend, manual focus it is!

Blue

Is it happening at all focal lengths, as I have found my K100D Super can be troublesome with shorter focal lengths

That wasn't me... it was my son
I've updated my avatar for the time being... hope this is better! LOL!
Matt

sorry Matt... you are all perfectly photogenic. Thanks for the as ever good advice!