Sigma Lens issues - any ideas?
Discussion
Doing a studio product shoot at college, using my D700 with Sigma 28-70 f2.8, we were getting some weird lens flare, coupled with images being generally desaturated. Swapped lens, perfect. Tried the sigma on a mates D90 and it became almost 'milky' through the view finder?! Any ideas what could cause this sort of problem with a lens and if it is home-fixable? LCE just told me at least 3 figure sum to service it 
The studio shot is almost certainly lens flare resulting from either direct or reflected light getting in the lens. Was it a high-key set? Did you have a lens hood on? A slight shift in angle, position or flagging off the lights usually sorts it. I suspect the latter is lens flare too.
Nah it's definitely a 'fault' of some kind - just dont know what or where! we tried it on different cameras at different angles and under different lighting, with / without hoods, flagged and masked lighting,all come out desaturated and indeed looking like I was shooting straight into a light source, even though I wasn't. We also tried different lenses under identical lighting and they came out perfectly.
Dropped it recently? Could be an air gap between elements that shouldn't have one. Suggest you deal with sigma direct for servicing or repairs, tariffs are here: http://www.sigma-imaging-uk.com/support/tarrifs.pd...
Personally I would strip it down and find the fault, but I couldn't recommend it unless you have had a bit of practice with lenses, they can be tricky things to work on, especially the more modern stuff.
Come to think of it, it does sound like a light leak, is the mount plate properly screwed on?
Personally I would strip it down and find the fault, but I couldn't recommend it unless you have had a bit of practice with lenses, they can be tricky things to work on, especially the more modern stuff.
Come to think of it, it does sound like a light leak, is the mount plate properly screwed on?
Edited by Cabinet Enforcer on Tuesday 27th September 20:00
Never been dropped, used a lot but I tend to treat all my equipment with kid gloves. Thanks for the tarrifs guide - I've not worked on a lens before full stop, but have lots of experience with micro modelling so used to small / awkward things - just how hard is it? what sort of nasties am I likely to find.
I think you summed it up perfectly though, it does look and react just like a light leak - in fact we spent ages trying to work out where the light leak was from in the studio before we realised it was the lens!!!
Metering is all working fine, it exposes very well really (apart from obvious excess light from whatever is causing the overall flare) although we were using full manual with hand held meter at the time I did try a few auto to gauge depth of the problem.
Crafty- that was another thought I had, but looking through the lens and stopping it wide open it looks fine inside, and there is no obvious problem that you can see there and no mistiness looking through the lens without camera attached
I think you summed it up perfectly though, it does look and react just like a light leak - in fact we spent ages trying to work out where the light leak was from in the studio before we realised it was the lens!!!
Metering is all working fine, it exposes very well really (apart from obvious excess light from whatever is causing the overall flare) although we were using full manual with hand held meter at the time I did try a few auto to gauge depth of the problem.
Crafty- that was another thought I had, but looking through the lens and stopping it wide open it looks fine inside, and there is no obvious problem that you can see there and no mistiness looking through the lens without camera attached
Davi said:
Blimey... Just took the top off the lens... Erm yeah that's a fiddly bugger no doubting!!! Managed to get the top few layers off and photographed AND reassembled - think that's a project for when I don't have a s
t mood on.
Can't say I didn't warn you t mood on.
You often need shaped rubber bungs to unscrew the front of the lens to get at the elements, also lens makers seem to love hiding incredibly small grub screws just where you aren't expecting them. You could try taking a few shots of a point source like an led, in a darkened room, it may give some clues to your problem.
yeah I noticed that thing with the grub screws. Sigma also seem to like making 4 screws look identical but under one placing a spring and ball bearing...for the first time in my life I'd been sensible enough to start dismantling over a black surface so I spotted the buggers when they came out! Really in two minds as to if I should go ahead. It's definitely not as good as it should be but it's only a serious problem in studio shooting - as a general portrait lens it's still kinda usable, just needs contrast and saturation tweaked a bit afterwards as it's really losing the low end depth.
ETA... this post would have made more sense if *someone* hadn't deleted their post...
ETA... this post would have made more sense if *someone* hadn't deleted their post...
Gassing Station | Photography & Video | Top of Page | What's New | My Stuff