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10-01-2010, 10:25 PM   #16
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ANY time you shoot a lens, really any lens, wide open at a brick wall you'll find faults. Doesn't matter if it's a lens created by Leica, Pentax, Nikon, Canon, Schneider, or anyone.

It's much easier to judge distortion looking at parallel lines, like those created by grout between bricks.

Case and point: when I got a new lens for my K-7 a while back, I read reviews that had it had about a stop of light's worth of vignetting when shot wide open. I did tests and found the review didn't lie. But guess what? I've never noticed the vignetting on any single shot I took other than the tests.

How about going out and shooting something interesting; we can critique your ability as a photographer much better than we can critique a lens that may or may not be a dud.

10-02-2010, 05:19 AM   #17
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I agree with you Ash that we should spend more time shooting than testing.

Can't recall the last time I took a shot of a wall.

My comments above were based on the Photozone test of the DA* 16~50/2.8 which indicated things were a little soft wide open. It also indicated barrel distortion was:

"At 16mm the lens shows fairly heavy barrel distortion (~3.6%) - this is slightly higher than average for a standard zoom lens but then we're also talking about 16mm here rather than the usual 17mm or 18mm setting. Beyond the extreme wide-end the distortion is actually very well controlled with slight barrel distortion at 24mm and slight pincushion distortion 50mm. "


The review further reported on "weak border performance".

"It is difficult to find a final verdict for the Pentax SMC DA* 16-50mm f/2.8 ED [IF] SDM. On the one hand it has some obvious problems like a weak border performance at max. aperture and very pronounced lateral chromatic aberrations (CAs). On the other hand it is really very sharp and contrasty at medium aperture settings (f/5.6-8) and many users may actually forgive the border problems at f/2.8 because you either stop down for conventional photography or rely on the (very sharp) center for shallow depth-of-field situations (e.g. portraits) anyway. The build quality of the lens is also a step up from the consumer grade Pentax lenses and the silent (although not overly speedy) SDM is an extra bonus on top. The pricing of the Pentax 16-50mm f/2.8 is fair relative to its performance and build quality."


Check the link below for the complete review.


Pentax SMC DA* 16-50mm f/2.8 ED [IF] SDM - Review / Test Report

Based on this review and reports of SDM failures etc. I debated long and hard before purcasing this lens. I've had it for about ten months now and after a fair bit of use I find it ot be the best zoom lens I've ever used. It occupies a permanent place in my bag.

Tom G
10-03-2010, 11:38 AM   #18
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Check out the shot below that I took with the lens in question (exp f/4.5 1/500, focal length 16 mm, focused on the fountain). Included are crops of the extreme right and left sides at actual resolution. I expect a little softness in the foreground since I'm focused on the fountain, but, the right side is farther away than the left yet the left side appears to me to be far more *in* focus. Is this symptomatic of de-centering/misalignment?
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