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06-09-2009, 01:01 PM   #1
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Problem with DA* 16-50mm at 2.8

Dear pentaxforums,

I've recently bought a DA* 16-50mm from amazon uk, s/n 9122075, and took a few phots at london taste of spain 2009. photos looks good at f/5.6 but at f/2.8 iso 100 39mm there is some strange effect (I'm quite new to the photography), the attached picture should show what I mean. Do you think I should return thislens to amazon for replacement?

All photos from the event available - here, this issue can be seen on each photo with high contrast.

Thanks for help

Attached Images
06-09-2009, 01:22 PM   #2
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I assume you are referring to the overall softness as well as the purple fringing. From what I have gathered (as I do not have one myself), this is pretty typical for the 16-50mm when shot wide open. Stopping down to f5.6 or lower will help with the fringing and resolution.

As for whether you should return the lens to Amazon, can't help there.

Good luck.
06-09-2009, 01:52 PM   #3
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What was the shutter speed on this shot?
If it was any slower than 1/30 (even with shake reduction mode on) OR you simply had a shaky/moving hand when shooting, motion blur can account for this.

As for purple fringing, it's a common phenomenon esp with Pentax lenses when using them in high contrast situations.

It's hard to tell from your slideshow whether other photos suffered from these problems - this one looks like a 100% crop while the slideshow photos are resized down (and are quite sharp).

Ensure your conditions are right and try again. Even at f/2.8, the centre of every photo should still be sharp with this lens.
06-09-2009, 02:12 PM   #4
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Hum, I've made many thousands of photos with my 16-50mm and virtually no (!) purple fringing or softness.... so I'm very pleased with my copy.
And I've done high contrast f2.8 as well many of times.

Bring it back, get yourself another copy, test it before taking it home.

- Bert

06-09-2009, 02:40 PM   #5
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Purple Fringeing along the silouette of the hat.

Possibility front focusing of the image.

Slow shutter speed for candid capture.

Though this zoom does suffer problem with focusing inaccuracy issue, this image seems to have a few areas that could be improved on. For example, get to know this zoom well to shoot a variety of situations as practice.
06-09-2009, 03:38 PM   #6
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Ah I see, I think I'll give the lens one more try before returning. The purple fringe - this is exactly what I meant
Thanks for all replies
06-10-2009, 10:28 PM   #7
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I just got my 16-50mm as well, and the purple fringing can be quite bad at f/2.8. I shot some crinkled foil and the CA was noticeable even at low magnification.

Thinking about exchanging through Amazon.
06-11-2009, 06:54 AM   #8
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My purple fringing is ok most of the time, but at 2.8 it can span a few pixels. In high contrast situation and at wide angle this will become more prenounced.

06-11-2009, 09:03 AM   #9
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I did do some tests with pine needles against blue sky and the CA was a lot less pronounced. Maybe it's just the foil doing some funky things that wouldn't normally be seen.

Here's the foil shot:


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