Some lens testing; some questions

Started May 7, 2013 | Discussions thread
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DavidWright2010 Senior Member • Posts: 1,019
Some lens testing; some questions

Lasrt week I got back the 8-16 lens I had send to Sigma NY for service. (Some of you may recall that I posted last year/this year photos that showed a distinct loss of resolution/sharpness in the 'this year' photo.) And it isn't the camera body (same symptom on an SD14 and an SD1M), nor one particular bad image. Anyway it was returned with a note that "ALL CHECKED OK  NFF CLEANED FRONT ELEMENTS NC". I took it out and tried some landscape photos - still poor.

Now, you'd think that when a customer returns an item and reports a problem, Customer Service would try to fix it. I've had some instances of great service from Sigma and some not-so-great; I'd put this one in the latter class.

I got to thinking that landscape shots are not the best for quantifying lens performance (but it's what 99% of my images are), so took some photos of my fence. Using the SD1M body, I shot at 8mm, 16 mm, and then my 18-50 DC EX Macro at 18 and 50mm, all at f/8, on a tripod with delayed shutter release. I didn't move the cam closer to the fence for the 8mm shot as at that close a range, the distance to the fence at the center and at the frame edge changes by about 2X. The 16, 18, and 50mm were taken at appropiate distances so that the FOV was constant.

The full FOV is this:

This view is of a portion of each 8, 16, 50 and 18 image (from upperleft, clockwise) showing the third board from the left where it crosses the steel cable - there's some interesting detail in the wood grain there.

(Note that in the 8mm version (upper left), I zoomed in twice as much as the others since I didn't move the cam.) But how can this be? the 8-16 is at least as sharp, and much better contrast, than the 18-50, which I have always thought was a pretty sharp lens.

Then I thought to include the DP2M in my comparison, so replaced the lower left image (the 50 mm one) with a DP2M image:

It's by far the sharpest, but what's with that contrast? The steel cable is bordered by a black line. It's as if I had dialed the contrast to MAX, but all images were processed in SPP 5.5.1 with default settings. (BTW, all the SD1 images had pretty good default color, but the DP2M reminds me of the SD14 - green, green, green everwhere.)

So my second question is, is SPP doing something special for DP image contrast? The default setting seems over-the-top to me.

And in case you missed it, my first question is, does anyone have an idea why my landscape image look mushy now, when this test image using the 8-16 looks ok? Could it also be SPP?


 DavidWright2010's gear list:DavidWright2010's gear list
Sigma DP1 Merrill Sigma DP2 Merrill Sigma DP3 Merrill Sigma SD1 Merrill Pentax K-70
Sigma DP2 Sigma SD1 Sigma SD14
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