17-50mm F2.8 at 17mm and F2.8 - CA and OOF areas expected?

Started Dec 17, 2017 | Questions thread
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Easy Rider
Easy Rider Senior Member • Posts: 7,593
17-50mm F2.8 at 17mm and F2.8 - CA and OOF areas expected?

Hi there. I was worried my Sigma F2.8 EX DC OS HSM was faulty as recent shots taken at F2.8 and at 17mm were very sharp on the main subject but everything to the sides and back were nasty and there was lots of CA.

However I've looked at other shots from the same session at 17mm and F5.6 and F8 and they are fine.

So would 17mm and F2.8 be expected to show nasty OOF areas and CA?

Here 's two examples, main subject very clear and sharp the rest of the photo is nasty.

17mm F2.8

Then two from same session at 17mm but F8 and not as bad though focus still looks off a tad..???

17mm F8

17mm F8

Normal performance in AF-S?  I don't have the efix reader where you can see the fouc points and I was shooting fast tbh. OS on.

I just want to know if this looks normal or faulty as I am selling it soon to an electrical shot but would never sell a faulty lens and if it does look faulty in some way I'd prefer to get it checked by a camera shop (one has offered o check it for free and give me a quote if it does need fixing) rahter than the electronics shop that may not test it properly and then some other photographer all excited about a good used lens and then buys a dud, I'd never do that.

I know this lens has lots of moving parts etc and has taken some knocks recently from people bumping into it when walking, so it could be the focus motor as the glass looks clean and scratch / damage free.

I just shot some shots of my living room at F2.8 and 17mm and tbh they were not worse than my 18-55 VR II at 18mm and F3.5, and that lens is in mint condition, barely ever used and stored well, so perhaps indeed wide open shots are the wide end of a zoom may be expected to have a lot of oof areas?

Anyway would like to know what any experienced people think looking at both the F2.8 and F8 versions here..  Cheers

 Easy Rider's gear list:Easy Rider's gear list
Canon EOS Rebel SL1 Canon EF-S 24mm F2.8 STM Adobe Photoshop CS6 extended Adobe Camera Raw 7
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