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10-07-2014, 08:08 PM - 3 Likes   #601
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f8, 1/125, iso100 8mm K-5 IIs

10-07-2014, 11:34 PM   #602
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QuoteOriginally posted by Digitalis Quote
Wideangle lenses need to be stopped down - it's the only way to effectively deal with field curvature and astigmatism that is inevitably in the corners. Even with the Sigma 8-16mm f/4.5-5.6 I will regularly stop down to f/11 so that the lens is sharp across the entire frame, diffraction be damned. Using a super wide angle lens you aren't going to get shallow Dof effects like you can with a 50mm f/1.4 lens - so wider apertures aren't all that important.

Here is the test from PhotoZone on a Canon ASP-C. It shows maximum corner resolution at f8 at 8/12/16mm. For maximum center resolution wide open is best. So, it seems that diffraction more than balances any gain from lower aberrations at small apertures.



10-08-2014, 01:23 AM   #603
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I will also point out that the Canon DSLR does have not only lower resolution but also an AA filter so performance will be somewhat better on a camera like the K5IIs. Also the photozone tests to not take field curvature into account - just about every ultra wide angle lens designed for smaller formats have it.
10-08-2014, 10:33 PM   #604
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QuoteOriginally posted by Digitalis Quote
I will also point out that the Canon DSLR does have not only lower resolution but also an AA filter so performance will be somewhat better on a camera like the K5IIs. Also the photozone tests to not take field curvature into account - just about every ultra wide angle lens designed for smaller formats have it.


Higher sensor resolution increases the loss from diffraction as well. I doubt that will move optimal aperture much. When not photographing subjects lying in a plane perpendicular to lens access, the effect of field curvature varies. In some conditions it will increase resolution in the corners.

10-08-2014, 11:27 PM - 1 Like   #605
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QuoteOriginally posted by civiletti Quote
the effect of field curvature varies. In some conditions it will increase resolution in the corners.
Providing you know how to take advantage of it and the geometry of the scene you are photographing conforms to it.

Last edited by Digitalis; 10-11-2014 at 03:31 AM.
10-11-2014, 03:05 AM   #606
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I got the wattle down
huge crop
8mm f6.3

Last edited by Transit; 10-11-2014 at 03:34 AM.
10-11-2014, 05:50 AM   #607
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QuoteOriginally posted by Transit Quote
huge crop
Effective!

10-11-2014, 08:28 AM   #608
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Nice silhouette shot.
10-11-2014, 04:21 PM   #609
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and no flare
10-11-2014, 10:18 PM   #610
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Thanks chaps
no flare and no sharpening, so likeing the K-5iis
10-12-2014, 07:03 AM   #611
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House Shapes

K3 Sigma 8-16 at 8

10-26-2014, 04:41 AM - 2 Likes   #612
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Pentax K5IIS - Sigma 8-16mm f/4.5-5.6 @ 12mm f/11 30s ISO 80
10-26-2014, 08:40 AM   #613
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Nice shot!
10-26-2014, 11:10 PM   #614
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Very nice Digitalis.
10-27-2014, 05:36 AM   #615
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Sigma 8-16 lightning

Great picture, Digitalis! Did you use a lightning detector?
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