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04-06-2008, 09:21 PM   #1
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Testing my 16-50

I just bought this lens from the B&H store in NYC.

I'm going on a climbing trip in a couple days and would like to decide if I need to send it back by then.

What is everyone doing to test their lens? Specifically the bf/ff issue.

Thanks!

04-07-2008, 10:34 AM   #2
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Also how quiet is SDM suposed to be...because this lens sounds just like all of my other ones
04-07-2008, 11:04 AM   #3
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http://focustestchart.com/focus21.pdf - Print out page 18

Test at various focal length and aperture.

Make sure the camera is at a 45 degree angle, leveled, and straightened.
04-07-2008, 11:53 AM   #4
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if you haven't upgraded to v1.3 firmware in your K10d, you're using the screw drive, not SDM.

04-07-2008, 12:22 PM   #5
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QuoteOriginally posted by nostatic Quote
if you haven't upgraded to v1.3 firmware in your K10d, you're using the screw drive, not SDM.
Yeah that was my first thought after posting that. SDM works now.

Here are the pictures from the test. They are all labeled with the focal length and apeture.

50mm: everything looks good
28mm: not as much back focus as 16mm but still apparent
21mm: not as much back focus as 16mm but still apparent
16mm: lots of back foucs from 5.6 down

So there it is...
What do you guys think :\

Is it the general consensus that this lens works well on the K20d?
04-07-2008, 12:28 PM   #6
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I think the images are dark and you're not square to the target. Is that handheld?
04-07-2008, 12:42 PM   #7
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Focus test chart is more or less to determine how much your lens/camera has BF/FF issue. To simply test to see if BF/FF occurs, i suggest you to shoot at a flat object (e.g. poster, newspaper,etc.). This would not only show if you have BF/FF issue, but also shows the corner's performance, another complain with the DA* 16-50. It's definitely easier to align your setup to shoot perpendicular to a flat subject than to angle 45 degree to the test chart.

The DA* 16-50 works better on a K20D than a K10D, according to general consensus. I don't even bother to test my DA* on my K10D. On my K20D, after the AF adjustment, every focals work fine.
04-07-2008, 01:07 PM   #8
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That was on a tripod at 45 degrees more or less. The corners seemed ok. I'll go try some flat object shots.

The K20d has the bf/ff adjustments right?

04-07-2008, 01:48 PM   #9
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Here are some full size test shots all 16mm 2.8

This first picture is focused on the white border (center of photo)

This on is focused on the middle newspaper (center of photo)

This one is focused in the center around the bottom left part of the black fence
04-07-2008, 02:22 PM   #10
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Okay I forgot to mention, you should have done an AF shot, then manually focus yourself in the same shot to see if you have BF or FF. And pick out a flat object with lots of texts or variety of images, that would be easier to compare. From your middle shot, I am certain that you have a problem with 16mm at f/2.8, I just don't know whether it's BF or FF. Here is my test platform/method (scroll down to the last post):

https://www.pentaxforums.com/forums/pentax-dslr-discussion/23985-k20d-front-focusing-issues.html

Of course at the widest end, 16mm, you should move closer to the subject so that there are texts at all corners.
04-07-2008, 02:59 PM   #11
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Thanks aegisphan. I did your test and I think the results speak for themselves.



It looks soooo good when the focus is right!!!

What would you guys do in this situation. One of the main reasons I wanted this lens was for the weather sealing. I might just return it. I'm not sure if I'll be getting the k20d anytime soon.

Has anyone exchanged with B&H before? How did it go?
04-07-2008, 03:10 PM   #12
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QuoteOriginally posted by Phazed Quote
Thanks aegisphan. I did your test and I think the results speak for themselves.
Looks quite similar to my previous DA1650, a very sharp lens even wide open, if focused properly. I think the problem is due to the SDM or the camera, not the lens alone. You can try the lens again w/ a K100D camera (which doesn't have SDM support) and see the difference. The DA1650 does work better on a K20D camera w/ much less BF problem at the wide end.

You can send the K10D camera and your lens to Pentax for AF adjustment, but they can't do much w/ a zoom lens.

The best cure? Go and get a K20D
04-07-2008, 04:52 PM   #13
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QuoteOriginally posted by Phazed Quote

Has anyone exchanged with B&H before? How did it go?
I have exchanged/returned several items over the years at B&H, including a DA* 16-50. B&H was excellent; one of the many reasons I always buy from them. The return/exchange process was straightforward and relatively easy. Best wishes.
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