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01-25-2010, 11:15 AM   #1
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DA14mm F2.8 - soft at F2.8?

Hi all,

Last time I tried the DA14mm at F2.8, I found it to be soft AND the focus never seemed to be dead on.

Is this normal for this lens? I found that I needed to stop down to F4 to get some sharpness throughout the frame. As for the auto-focusing, maybe it's the "wideness" of the lens that makes it sometimes get the focus right? Or did I test a bad copy?

01-25-2010, 11:27 AM   #2
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QuoteOriginally posted by dugrant153 Quote
Hi all,

Last time I tried the DA14mm at F2.8, I found it to be soft AND the focus never seemed to be dead on.

Is this normal for this lens? I found that I needed to stop down to F4 to get some sharpness throughout the frame. As for the auto-focusing, maybe it's the "wideness" of the lens that makes it sometimes get the focus right? Or did I test a bad copy?
Here's a sample from photozone at f/2.8:

http://www.pzimages.com/8Reviews/lenses/pentax_14_28/samples/IMGP4506_acr37.jpg

BTW, the field curvature of this lens is "wavy."
01-26-2010, 06:42 AM   #3
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QuoteOriginally posted by asdf Quote
BTW, the field curvature of this lens is "wavy."
I wonder whether the new lens correction feature in the K-7 and K-x would eliminate this moustache distortion?
01-26-2010, 06:44 AM   #4
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QuoteOriginally posted by audiobomber Quote
I wonder whether the new lens correction feature in the K-7 and K-x would eliminate this moustache distortion?
I'm referring to the area in focus, actually. EDIT: Macro lenses have a flat field curvature which makes them ideal for ISO resolution chart tests, brick walls and cereal boxes. Otherwise, the borders and corners can easily fall out of focus, making such tests unfair.

diglloyd: Understanding field curvature

As for the distortion, there was a thread about this recently...It turns out the cameras don't do a good job removing it, but PTLens does.


Last edited by asdf; 01-26-2010 at 06:50 AM.
01-26-2010, 08:03 AM   #5
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QuoteOriginally posted by asdf Quote
As for the distortion, there was a thread about this recently...It turns out the cameras don't do a good job removing it, but PTLens does.
My K-x does a great job removing distortion on the DA 18-250mm.

The reason I asked about the DA 14mm is that the distortion is not simple barrel. It goes from barrel to pincushion, so is not easy to correct with PT Lens. I'm wondering what the camera's lens correction can do.
01-26-2010, 08:07 AM   #6
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QuoteOriginally posted by audiobomber Quote
My K-x does a great job removing distortion on the DA 18-250mm.

The reason I asked about the DA 14mm is that the distortion is not simple barrel. It goes from barrel to pincushion, so is not easy to correct with PT Lens. I'm wondering what the camera's lens correction can do.
In PTLens, you press "OK" to correct the distortion. Is that "not easy"?

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/87494-super-wi...m-12-24mm.html
01-26-2010, 08:33 AM   #7
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QuoteOriginally posted by asdf Quote
In PTLens, you press "OK" to correct the distortion. Is that "not easy"?
I was going by this quote from Photozone: "Distortions are relatively well controlled but quite wavy thus somewhat more difficult to correct via imaging tools." But I guess with PT Lens having lens specific correction it does the job without the trouble. I will definitely have to get PT Lens and see what it does for defishing my 10-17.
01-26-2010, 08:35 AM   #8
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QuoteOriginally posted by asdf Quote
Here's a sample from photozone at f/2.8:
That's a damn nice photo.

01-26-2010, 12:49 PM   #9
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Some quick answers:

My DA 14 would hunt sometimes when focusing near infinity on the K100DS. Other than that it worked quite fast and ok. On the K-x I have no problem at all.

The K-x in camera lens correction corrects only for the barrel distortion and not for the pincushion distortion it seems.

Regarding sharpness, I recently made a 50x70 cm print of a photo taken at f3.5 with the subject in a corner, and it turned out really well. With proper focusing it is really sharp, more than enough for real world use.
01-26-2010, 01:29 PM   #10
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ah, maybe the copy I tried out was a bit weird, or I'm not used to such a wide angle field of view.

I think the focusing was the main thing. It just wasn't tack sharp on my K10D. Definitely had BF.
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