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Re: [OM] dance photo shoot

Subject: Re: [OM] dance photo shoot
From: Moose <olymoose@xxxxxxxxx>
Date: Mon, 26 Jan 2009 15:57:25 -0800
Chuck Norcutt wrote:
> And for a contrary opinion for full frame on a 5D
> <http://www.slrgear.com/reviews/showproduct.php/product/48/cat/23>
>   

Sheesh! I looked at that site last night, didn't see the FF tab and went on.

> Awful edge performance until you get to f/8, f/11. At f/11 it gives 
> consistent good (but not great) performance across the full zoom range. For 
> Canon shooters SLR Gear recommends the Canon 17-40 over the Tamron 
> 17-35. <http://www.slrgear.com/reviews/showproduct.php/product/31/cat/11>
>   

Interesting stuff. The 6 user reviews of the Tamron average 9.0 for IQ, 
the 36 for the Canon average 8.92. At FM, 25 reviews average 8.8 for 
Tamron and 431 average 9.0 for the Canon. It appears the huge 
differences in the test results don't correlate with user experience.

One factor may be:
 "/Far-field performance (Especially for wide-angle lenses)
/Given the finite size of our studio and the targets available to us, 
the camera is always relatively close to the test target. (Especially 
with wide-angle lenses.) Good lenses generally have behave similarly at 
medium and long focal distances, but "far field" performance could be 
different for some models. - Pay attention to the reports and sample 
photos offered by other readers for this information."

At 17mm, the subject to lens distance must be very short.

I've just browsed through some of my images @ 17mm or so with this lens 
No definitive conclusions, but several observations.

- I don't have very many images suitable for evaluating far zone 
sharpness, especially upper corners. In most shots, either there is no 
detail in the corners or it is OOF anyway from DOF.

- Edge softness isn't much problem even @ f2.8, and gone by f4. The more 
correct term for the area of concern would be corner softness.

- The left upper corner of mine is softer than the other three. The 
three are good way out almost to the deep corner. The other can be 
pretty fuzzy a bit further in, depending.

- I say 'depending' because it appears the corner softness may be 
largely due to field curvature. So the results depend in part on the 
'shape' of the subject. Most of the shots I took in Hearst Castle had 
edges closer to the camera than the center, and I think the field 
curvature worked in my favor.

- Field curvature may vary quite a bit with focal distance. Just a hint 
from too few images to be sure.

- I lost many of the far upper corners to linear lens and perspective 
distortion correction, so they don't figure into final images at all.

I may look at this some more, but I have to say I'm still impressed with 
the lens overall. I will try to remember to stop down more where the 
light allows. But honestly, something over 99% of image area and images 
are nicely sharp.

Moose
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