Sigma 30mm 1.4 front focus

Today I went out to get a sigma 30mm 1.4. I asked to try the lens.
Tested it on a bit of writing on some random box there, and it front focused about 3mm. I tried this a few times, and every time I got more or less the same result.
Also took some shots parallel to the box, and ALL the attempts (both mine and the guy working at the store) were extremely soft.

I eventually tried 3 more samples which were all more or less front focusing.

I ended up buying a 50 1.8, but when I tested that more carefully at home, it also front focused, as did my Tamron 17-50 - which didn't really have any of the issues before.

I made some comparisons to the autofocus and the focus I would get with manual focus in live view. All the live view shots were sharp (on both lenses) and the AF shots were a lot softer.

I'm now starting to doubt my 40D... however, as I was searching for all of this, I came across some other users (though mostly pentax stories) of cameras front focusing on tungsten light... Did my 40D all of a sudden get focus issues or maybe something broke down?

I have trouble believing that all of a sudden 6 lenses I try are front focusing, both near MFD as like 4 meters away.

I'll try to do some more tests with daylight and post samples tomorrow

This is a very common problem with that lens. It took me 3x to get a good AF copy. Optically it's awesome but the focus inconsistency problem plagues this model.

My Sigma 30mm never worked well with my 40D, and didn't with the 50D I later bought until I did the micro-adjustment. I then sent my 40D in to be checked, and Canon adjusted it. When it was returned it worked almost as well with the Sigma as the 50D does.

So I think mine was the camera, not the lens .......

Maxdave

swidjaja wrote in post #8085929
This is a very common problem with that lens.

The OP is describing a problem with the camera or lighting. Not the lens.

Tony-S wrote in post #8086082
The OP is describing a problem with the camera or lighting. Not the lens.

Yeah, my topic title may have been misleading :P
But it turned up while testing Sigma's. Out of the 4 I tested, 2 had a MUCH heavier degree of front focus... I'm now thinking the other 2 might have been good

My 40D is due back from recalibrating - it front focussed wildly with the Sigma 30's I tried, but close inspection of shots show it was front focussing to some extent with all lenses.

philthejuggler wrote in post #8086192
My 40D is due back from recalibrating - it front focussed wildly with the Sigma 30's I tried, but close inspection of shots show it was front focussing to some extent with all lenses.

Did you also send lenses in? I don't mind sending my 100mm macro and 50 1.8 in with the camera if it comes to that, but I prefer to leave the none-canon lenses here...

To add to my confusement, I just did a re-test in daylight (cloudy). The Tamron still front focused, the 50 1.8 still front focused, but seemed way less dramatic. The 100mm macro was dead on...
I'll have to compare the lenses with a focus chart and add my friend's lenses and 30D to the test >_<