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03-08-2009, 09:46 AM   #1
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DA* 16-50 fringing, back focus help (pics?)

I just got this lens yesterday. I am kinda paranoid about the issues I read. It is PRICEY, so I don't NOT want to miss IF this is the case with my new lens before I can return it.

Does anyone have picture's of what these 2 things look like? And what is the easiest way to spot it?

Never dealt with them before, so no clue where to start looking! =)
TIA!!

03-08-2009, 11:11 AM   #2
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Here are some samples..It is a great lens. I have used it on 75 percent of all of my published working shoots.

PENTAX Photo Gallery

and all over this gallery, especially from page 10 onwards:

PublishedWorks Photo Gallery by Benjamin Kanarek at pbase.com
03-08-2009, 01:02 PM   #3
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Correct me if I'm wrong...

I got my DA*16-50 when quality control discussion was all the rage; fringing wasn't getting that much attention. I was relieved to find that my copy seemed to be free of the focusing issues (which as I understand it--someone correct me if I'm wrong--would translate into the focus quite simply being either closer or further than the confirmed AF focus was supposed to place it).

As for fringing...

It would be rather humiliating to post images of purple fringing, only to be corrected with "that's not PF at all"! Everyone talks about it but showing examples is much rarer. That said, as I say I got my copy without a thought to fringing and none of my real-life shots were spoiled by fringing (I haven't pixel peeped them to see where there might be examples). But when testing recently against prime 28mm lenses (and generally primes should perform better) I found the DA*16-50 as sharp or sharper, but exhibiting a bit more purple fringing. Here are some quick and very dirty (literally!) hand-held shots that illustrate:

At f/2.8, bright reflections off a glossy surface have an obvious purple-indigo "glow" around their edges, obvious (but depending on taste/need, perhaps tolerable) in a view of the full image:
View Picture EXIF
Name:  PF at 2.8.jpg
Views: 321
Size:  66.1 KB
and at 100% crop:
View Picture EXIF
Name:  PF at 2.8 crop.jpg
Views: 324
Size:  93.2 KB

Stopped down to f/4 (typical of all lenses, PF goes away as you stop down) it's much less obvious when viewing whole image, but a 100% crop shows it's clearly still there:
View Picture EXIF
Name:  PF at 4.0.jpg
Views: 245
Size:  76.4 KB
View Picture EXIF
Name:  PF at 4.0 crop.jpg
Views: 259
Size:  107.8 KB

By f/5.6, it's pretty much gone even at 100% crop (oh, traces I suppose...):
View Picture EXIF
Name:  PF at 5.6 crop.jpg
Views: 282
Size:  115.9 KB

As far as I know this fringing is a lens characteristic, not a defect of only certain copies (right? anyone going to correct me?), is found to some degree on most lenses, and is really only brought out when shooting with wide apertures at something with bright highlights (e.g. glare from sun off metal, water, etc.) and can be avoided by shooting technique.

Like I say, as "bad" as the fringing may be on my DA*16-50, I find it doesn't hurt my real-life shots (even without making an effort to avoid it) and my love of the lens is in no way blunted by this issue. (By contrast, fringing in shots of birds on the water wide open (to get acceptable shutter speeds) with my Tokina 80-200/2.8 did blunt my enthusiasm for that lens, but I wasn't & won't be shooting birds on the water with my DA*16-50, and even if I were I could afford to stop it down where I couldn't spare the speed for telephoto shots with the Toki).
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