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01-20-2014, 10:57 AM   #76
ogl
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I don't understand PF's review. My short using of DA20-40 says that it's the one of the best zoom Pentax ever made.
The sharpness as the best prime lenses. I think you need to test focus of PF's copy and retest lens in RAW.

I can confirm AF problems even with K-5IIs. It's suprise for me.


Last edited by ogl; 01-20-2014 at 11:10 AM.
01-20-2014, 11:27 AM   #77
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QuoteOriginally posted by ogl Quote
I don't understand PF's review. My short using of DA20-40 says that it's the one of the best zoom Pentax ever made.
My experience of this lens agrees with yours.

I concur that focus problems are one cause of the perceived weakness in the PF review.
In addition, I suspect that the first copies of this lens were still "beta" versions.

We now have a lens club for this lens,
as a more stable home for sample images and discussion:

https://www.pentaxforums.com/forums/122-lens-clubs/247859-da-limited-zoom-club.html
01-20-2014, 12:14 PM   #78
ogl
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Thank you. I will join soon.
01-25-2014, 01:00 PM   #79
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Thanks to ogl for your very useful test images, which immediately suggest that the optical problems evident in the review test shots are not representative of all copies of this lens. Both shots show good cross-frame sharpness considering they were taken at f4.5. I'm guessing that the small amount of edge softness which is present will improve on further stopping down.

Whether the problem in the review images was due to focus issues or a bad copy of the lens is hard to be sure, but this gives me heart that at least some copies of this lens are worth the money.

It is my opinion that for reliable evaluation of lens sharpness in test shots, it is essential to 'bracket' focus at every aperture tested. Focusing systems, whether via AF, the optical finder, or live view, are imperfect. Without taking several shots with slightly varied focus, it is impossible to determine whether optimal focus has been reached, and you are effectively testing the focusing system as much as you are the lens. Focus bracketing would also help to determine whether edge softness is down to curvature of field or actual lack of resolution. This is not intended as a criticism of this review because some form of focus bracketing may have been used, but I'm pretty sure that many 'sharpness test' images posted on the web have not had focus optimised in this way.

01-27-2014, 01:49 AM   #80
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I just received my copy of the DA20-40 this week-end. I must say I'm impressed. Sharpness is more than good enough for me, looking at 100% at a few of the shots taken with my (also new) K-3. The bokeh looked very nice to me as well. I think I will be using this lens wide open more often than I ever did other standard zooms. I should compare more systematically with my other glass someday to be sure, but for now my conclusion is that this DA20-40 is destined to become a classic.

Wim
01-30-2014, 06:28 AM   #81
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There is a new review of DA 20 - 40mm on ephotozine.com. Looks good
They have tested all DA Limiteds as well.

A
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