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08-17-2012, 02:48 PM   #31
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but that is a lot of shipping cost if send several lens and body to sigma......

08-17-2012, 07:20 PM   #32
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I drove over to CRIS this afternoon and picked up my camera and lens. They were all ready, right on time as they indicated. The notes on the service form indicated that they adjusted optimum resolution focal point, cleaned and checked to manufacturer's specifications. The camera body was used for testing purposes only.

I took some pictures after I got home, of the same scene as I did on Monday. I am trying to past them side by side for easier comparison. Resolution did not change - Not getting the sharpness of an 85mm lens at 8mm. That was not an expectation. I usually never really pixel peep, but it does appear that the individual pixels of the infamous fire hydrant were a bit better defined by what 10~15%. I have no quantitative way of measuring that - so it is pure speculation.
  • Am I happy with the results - Absolutely! Its as good as its ever going to get. The leaves on the Ocotillo are now sharp as opposed to being blurry blobs. The lens no longer focuses beyond infinity.
  • Did I learn something - Sure did - and it was all positive. In talking with the girl at the front counter, she was saying that they get a lot of Sigma in that is within a week or two of purchase, for "tuning" - but once they are set up, then seem to never come back. On Wednesday, they said, that they needed to check to make sure that they had everything that they needed, since "we don't see too many K mounts, and this is the first 8-16 in a Pentax mount we have seen".
  • CRIS put a rush on this for me - and for that I am very appreciative of their additional effort.
  • It was all done under Sigma's warranty.
  • They did have to set my camera up for the calibration of the lens, so now I am going back and trying to remember all the items that I had set. I think I have most of them. But still now want to run each lens I am going to take with me so that I have no surprises. I had to re-enable the manual aperture ring.
  • Did it make a noticeable difference? When you look at the entire frame, I doubt that you can see it, however that depends somewhat on the relative distances being depicted in the image. Panoramic landscape, no. Interior shot possibly.
  • That now brings up the various lens reviews, indicating that a lens this wide is nice and sharp. Its all relative.
  • Now I need to figure out the best way to apply this lens, for the best results.

I'll be adding more to this as the evening goes - but I want to go shoot the sunset and check the colors...

OK, here are the images, the one Monday, and then the one today. I know the lighting is different, that's the best I could do on short notice. Is there any real difference, when one tries to compensate for the light. Well, I went pixel peeping and at 800% the blobs looked better defined. The lens is not designed for pixel peeping.

What the lens is designed for is taking in the wider view - and I think that it does that pretty well.

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Last edited by interested_observer; 08-18-2012 at 02:12 AM.
08-18-2012, 05:20 AM   #33
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Good!
08-18-2012, 05:36 AM   #34
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QuoteOriginally posted by interested_observer Quote
...at 800% the blobs looked better defined.
800%???

Even at 100% you are using a magnification that corresponds to a 11x16 high-quality print (assuming the K-5 and 300dpi).

What is the magnification for the two hydrant shots and at what f-ratio did you take them?

In particular in the corners, all wide angle lenses struggle especially wide open. From what I've seen the Sigma 8-16 is very sharp indeed for a wide angle and you were probably expecting way too much.

08-18-2012, 06:51 AM   #35
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QuoteOriginally posted by Class A Quote
800%???

Even at 100% you are using a magnification that corresponds to a 11x16 high-quality print (assuming the K-5 and 300dpi).

What is the magnification for the two hydrant shots and at what f-ratio did you take them?

In particular in the corners, all wide angle lenses struggle especially wide open. From what I've seen the Sigma 8-16 is very sharp indeed for a wide angle and you were probably expecting way too much.
Morning Class, For both images I used 8mm. The first one was at f7.1, ISO 80, while the second one was f11, ISO 100. This is how I discovered that the body had been reset, since I could not dial the ISO down. The difference in aperture I did not notice until last evening. On this lens, I am not sure that it makes that much difference, since by f5.6 the Depth of Field is pretty much the whole scene. The crops were at 100%

There is one utility that I have where by you can expand the image by 8x (or 800%). Useful? Never really noticed it before, as this is the first time that I saw this capability. Used it just to see what the real difference was if any. What I saw was the "before" was more fuzzy than the "after". When I was looking, I selected something that would have some sort of definition near the center - just because difference between the center and the edges. As I wrote previously, I was sorta of expecting sharpness to be between my 12-24 and my 10-17FE. And that was indeed one of the questions in my mind all along - in terms of the focal length, is this a reasonable expectation. The primary indicator was over focusing at the infinity end.

08-18-2012, 06:56 AM   #36
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...I feel there is no big difference between the two test photo
08-18-2012, 10:08 AM   #37
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While distant subjects shot at 8mm are not going to look great when pixel-peeping, have you gotten a chance to evaluate the sharpness of near subjects? I've always been pretty impressed with how sharp my 10-20mm is when used up close. Here are a couple test shots from the other day, both shot at 10mm.

The pictures aren't supposed to be anything special; I was just checking the calibration after I got my K-30 and my lenses back from Sigma. They were both shot RAW at ISO 400 without any noise reduction applied in development. The picture of the turn signal had to have the exposure increased by 1.5 stops in development, so I guess it's probably more like an ISO 1200 shot in terms of noise. It was shot with the lens at the minimum focus distance, which means the front element was only about 4 or 5 inches from the side of the car.

If you click on the images, you can view the full-size uncropped 16MP version.



08-18-2012, 11:41 PM   #38
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Hi,
QuoteOriginally posted by interested_observer Quote
The first one was at f7.1, ISO 80, while the second one was f11, ISO 100.
That may give the second shot an advantage, depending on where the resolution of that lens peaks and where the focus point was.

I believe at 100% (and some capture sharpening applied) your shots should look better. Maybe a Sigma dealer would know more about how this lens is supposed to perform compared to CRIS?

But maybe your copy is fine and you may still have focusing issues (see below).

QuoteOriginally posted by interested_observer Quote
On this lens, I am not sure that it makes that much difference, since by f5.6 the Depth of Field is pretty much the whole scene.
The DOF characterises acceptable sharpness for a standard viewing position. If something is only just within the DOF, it won't look sharp at 100%! Only a small region before and after the actual focal plane will look sharp at 100%.

Edgar_in_Indy has provided some nice shots that are in line with what I would expect from this lens. Maybe you can nicely ask for 100% crops (from areas that are spot on in the focal plane) so that you can judge the sharpness for yourself.

08-19-2012, 04:58 AM   #39
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QuoteOriginally posted by Class A Quote
Edgar_in_Indy has provided some nice shots that are in line with what I would expect from this lens. Maybe you can nicely ask for 100% crops (from areas that are spot on in the focal plane) so that you can judge the sharpness for yourself.
If you're referring to crops from my images, there's no need to ask. Just click on the images to view/pixel-peep the original, un-cropped, full-size images.
08-20-2012, 11:03 AM   #40
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With Sigma 8-16 at 11mm and f14

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