Softness / Focussing Problem on Sigma 24-70DGEX Macro?

I had a big shoot to do at a...erm...'gentleman's club' on Saturday night to photograph each of the dancing ladies for the club's website (hey it's a tough job you know!).

I used it as my opportunity to try out my Sigma DG EX 24-70 Macro lens...I've been using it for product photography with a couple of flash heads with lovely results, but most of these are reasonably close up shots, so not really using the full range of the lens.

With this job I needed to take posed shots with three flash heads and softboxes, fairly close up head and shoulders, a mid-range top part of body and a full length shot. The first two look superb, the images really leap at you but the full body shots using the 24mm end of the lens are really dissapointing, and very soft - to the point of being out of focus.

I was using f/11 so I wouldn't think that it's a focussing issue - but does anyone else have any ideas that might point me in the right direction?

I phoned Sigma UK, they just want me to send the lens back for a month and maybe my camera too. Not a lot of use for someone who needs to make a living from it!!

Help greatly appreciated.

Greetings. You might want to have Sigma take a look at it. There are copies that front-focus at the wide end (though not usually at f11, more like f2.8 ). With my copy I sent it in and they updated the main flexboard and got focus bang on. When the lens is "on", it's stellar. But obviously misfocusing isn't going to bring lovely results. Have Sigma check it out.

The only thing in this moment I can think about is the type of AF you have used, may be did the camera choose a wrong target? The AF relays in contrast diference, Can you see in that photo a "clear" or focused object? Or could be the influence of any reflection or may be infrared command through the viewfinder / Lens disturbing the AF?. Can you checked outside, with natural light to check if the problem persist? Make shot at 24 mm f/11 and check if you have OOF images.

That´s I should do if I were you. Just to be sure if the lens has a problem or not. Even I should try shots with the focus chart patterns at 24 & f/11 to check it. Then if the problem persist, Sigma is the solution.

My copy works very well and it´s extrange or dificult to understand what happened to you because in optics when you close the shutter you get sharper and more DOF until f/16 or so. If outside, with naural light, the lens performs fine, then something in the nightclub enviroment can disturb your composition.

Just guessing ....

Thanks, I think you're right - the lens is only a few months old so I think it should go back to them for checking - just don't fancy being without it for a month, as it's my lens of choice for a lot of the product work I'm doing right now and using it means no real processing in PS, which is great if you've got hundreds of images in one session...but it's not much use to me unless it's sharp at all lengths.

I agree with you about the lens being stellar - the photos of the girls head and shoulder shots are some of the best I've seen come straight out of my camera...of course having three Bowens heads on the go probably helped a bit too!! Which made the wide shots so much more disappointing.

Good point on that. I was (as I always do) use single point focussing...I can't be doing with the camera guessing where I want it! In these instances I was using the centre point to focus on the girls' eyes then with finger on the shutter release moving down to fill the frame with her. I didn't hear the lens hunt for a new focus point, but I suppose it might have done. But even if it did as I was at f/11 I would guess that it wouldn't have made much difference as there should be lots of DOF to play with. But I will experiement with different focussing points to see if that might be an issue.

I tried playing about with the lens in the back garden today in afternoon sun (we do occasionally have that here in England!) and I couldn't reproduce the problem with a cuddly toy, but then he was fully clothed!

You might be on to something with the club environment - it was abnormally warm in there, but we were in a separate section so there was no cigarette smoke or similar that might cause problems - and the lighting was sweet as you like from the Bowens heads.