Q for DK re Sigma 10-20

[ianmiddy]

David - saw the following on a DPR thread and wanted to ask about it, but didn't want to appear contentious -

"> was wondering about complimenting it with the Sigma 10 20mm? 16mm
> would then be in the middle of its range and i would appreciate a
> wider angle. Is it of compatible quality to the SAL1680?

No, it's not (it suffers from quite strong flare if used into the light) and there will be just as strong CA, plus a full f-stop lower maximum aperture."

I've been generally very happy with my 10-20 into the light and with dark objects against light, but an wondering if I've just not come across the same conditions that cause your comments - here's a few shots that I think exhibit good results and I was wondering if you could suggest if I just have a particularly good copy or if they're just not very taxing examples:

http://img.photobucket.com/albums/v643/ ... Custom.jpg
[resized to 6mp to get past Photobuckets free 1mb max]

http://img.photobucket.com/albums/v643/ ... Custom.jpg

http://img.photobucket.com/albums/v643/ ... 8Large.jpg
[Know this has a flare 'diamond', but didn't think it was too bad for f8]

These are all resized using the XP-powertool - maybe not the best approach, but the quickest to get them to more manageable filesizes at large/full-size - all are un-PP'd A100 camera-jpgs with 0/0/0 Contrast/Sat/Sharpening - I know you suggest maybe using -2 sharpening and then PP, but I'm lazy !

Thanks for any comments you're able to make.

IDM

[David Kilpatrick]

That sort of shot is not what produces the flare. See:



It's if the sun strikes the curved front element at the wrong angle from out of the picture. Including the sun in the shot is generally OK.

David

[ianmiddy]

Thanks for the reply, David - been away & only just remembered to check this thread, lol...

...will have to give the 10-20 a few tests trying to duplicate the condition you describe - maybe more likely to occur nearer the equator than I usually shoot ! - although will be using it in Croatia at the end of the summer, so will be well to know what to watch out for beforehand.

Thanks again.

[oh - and hope they let you back into DPReview sometime soon - I just have a bookmark to your threads, rather than reading all the Sony DSLR ones!]

IDM

[David Kilpatrick]

That was one unlucky shot in a hundred. It does not happen with the Tamron 11-18mm (you can still get flare shapes like most lenses) so it came unexpected from the Sigma in this grabbed shot.

David

[ianmiddy]

It's if the sun strikes the curved front element at the wrong angle from out of the picture

Do you think the effect may be reduced with a UV filter fitted [which I do] ? - only I tried some shots with the mid-morning sun just out of frame [top left] but certainly falling on the glass past the lens-hood, but without ill-effect...

...or might it be worst in very bright, but hazy, conditions ?

Cheers

IDM

[David Kilpatrick]

I don't think a filter will ever reduce flare, but the rim of the filter might act like a mini lens hood and just prevent this exact effect from happening. As I say, it happened on only one single frame during this trip, but it was a type of flare I can not remove or retouch. I've worked with the 11-18mm lenses (KM, Tamron and Sony) much more than with the Sigma, and for two of the periods I have had using the Sigma, the bodies have been 1.6X (Canon) and 1.7X (Sigma) sensor factors - this time it was on a Nikon (1.5X like the Sony bodies).

As you will realise, I have a bit of experience with both lens designs and I've used five 11-18mms in various fits in total, four 10-20mm Sigmas. Both lens types are great, with the Sigma showing a little more barrel distortion but also a slightly wider view. My preference for the 11-18mm has nothing to do with this flare example, it is connected only with the image geometry for my type of subject - I happen to take many pictures in landscape format which are architectural and have verticals close to the edge.

David

[ianmiddy]

...the Sigma showing a little more barrel distortion but also a slightly wider view. My preference for the 11-18mm has nothing to do with this flare example, it is connected only with the image geometry for my type of subject - I happen to take many pictures in landscape format which are architectural and have verticals close to the edge.

Thanks for this, David - unfortunately, I'd already got the 10-20 for a trip to Skye last summer before the Jessops cheap sell-off of the 11-18s, and couldn't justify having both, but I do take your point re the distortion - it's certainly a very 'odd' type at the edge when set at 10mm [I've tried correcting it in HeliconFilter, and it needs some very strange combinations], although seems to get a little better by 12-13 - remember your geometry example of the 11-18 in Photoworld and can see the value there, although most of my wider stuff tends to be landscape work, so not as much of an issue...

Will just have to keep any eye open for the flare when in bright sun and any 'unrepeatable' shots !

Cheers

IDM