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View Poll Results: Is this DA*16-50mm good or bad?
Keep it -- it's good. 2388.46%
Return it or send it in for repair. 311.54%
Voters: 26. You may not vote on this poll

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03-28-2008, 02:13 AM   #556
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The corners look pretty bad to me.

I didn't do similar test on mine, only checked the center. Seems okay.

03-28-2008, 04:47 AM   #557
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Did you conduct this test because you have taken a lot of photos with this lens that look like they have soft corners, or just to satisfy your curiosity?

The reason I ask is because I'm curious if this lens is showing obvious image quality problems in regular photos. Sure, it might not be the best lens for photocopying pages of text, but that's what a short macro prime with a stable tripod or copy stand is for.

For example, one of my favorite lenses is the Sigma 24-70mm f/2.8 DG ... which I have purchased for THREE lens mounts over the last 4-5 years (Nikon, Canon, and Pentax) and is my "go to" lens for most of my work. The Sigma was also the only lens that I chose to bring with me to the hospital when my daughter was born.



My point is, as much as I love the Sigma I doubt it would perform any better (and probably WORSE) in this type of test than your DA* 16-50mm.

We tend to pay a lot of attention to "test photos" when a new lens comes out, but in my mind a lens only has serious problems if things like lack of edge sharpness, poor contrast, inaccurate color tone, and harsh bokeh are obvious in typical/real-world photos.
03-28-2008, 05:03 AM   #558
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Your baby daughter is beautiful.
03-28-2008, 05:40 AM   #559
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Thank you for your replies so far.

As I am considering purchasing one of theses lenses myself I was concerned with high number of lenses I have read with focus defects.

The DA* is Pentax's line of excellent optics costing significantly more, so one would hope to see some improvement.

I have taken pictures of my kids/pets & friends babies using my Sigma 17-70 F2.8-4.5 & Sigma 24-60 F2.8, compaired with the DA*16-50 you would be hard pressed to tell which lens took which picture.

I guess this is why we have test charts to give us some feedback on the quality of the lenses.

Which brings me to the question, of thoes people who have exchanged thier lens because of focus defects, would the lens I tested be deemed as acceptable compaired to what you have?

Cheers

03-28-2008, 05:41 AM   #560
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I forgot to add,
Very nice photo JJJ
03-28-2008, 06:03 AM   #561
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It's clear to me, the right border is sharper than the left border.

Kyrios
03-28-2008, 06:10 AM   #562
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QuoteOriginally posted by kyrios Quote
It's clear to me, the right border is sharper than the left border.

Kyrios
From 5.6 onwards left corner is sharper than right corner.

Post a real shot and let us see.
03-28-2008, 06:15 AM   #563
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Corner wide open is prone to be out of focus and not that practical in most styles of photography. I would prefer a nice creamy bokeh at f2.8; for scenery shots, f8 would be a must.

The lens now passes the test of BF on k20d and I think the cost of buying this zoom is finally justified.

03-28-2008, 07:50 AM   #564
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Odd how the bottom right seems to actually degrade as you close down the aperture. I guess I'm used to primes as I would be uncomfortable with that, sorry though I don't have a 16-50 to relate your findings. FWIW, I can relate with the testing of gear though. I like to know that what I paid for is more than a good feeling.
03-28-2008, 08:02 AM   #565
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I agree no lens, particularly zooms will give you egde to edge sharpness @ F2.8, that would be asking for too much.

But you pay a premium price for F2.8 so stopping down to F4 - 5.6 you would expect a big improvement.

I also like a smooth bokeh of an object that has depth, but it has little to do with two dimentional target on the same plane.

As in my OP, it's not my lens so it will be up to my father if he keeps the lens or not.
If it was me I would be inclined to try one more copy, if it's the same, accept the fact or sell it & use either of the two Sigma lenses I have.

Anyway, thank's for all the replies.

Del
03-28-2008, 08:10 AM   #566
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I'm considering getting this lens, and for what it's worth, those results would not be acceptable to me. I've seen much better test shots from this lens.

Matt
03-28-2008, 09:09 AM   #567
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QuoteOriginally posted by VHDEL Quote
I agree no lens, particularly zooms will give you egde to edge sharpness @ F2.8, that would be asking for too much.

But you pay a premium price for F2.8 so stopping down to F4 - 5.6 you would expect a big improvement.

I also like a smooth bokeh of an object that has depth, but it has little to do with two dimentional target on the same plane.

As in my OP, it's not my lens so it will be up to my father if he keeps the lens or not.
If it was me I would be inclined to try one more copy, if it's the same, accept the fact or sell it & use either of the two Sigma lenses I have.

Anyway, thank's for all the replies.

Del
Then it would be better to ask some of the people with good copies to post of these newspaper test. It would provide us the rough idea of what to expect from a good copy.

Personally, I'm fine with the corner softness at wide open for these kind of zooms. But I do expect a good to high resolution for center cause, after all, that's the main why I bought the fast zoom for.

So I assume you don't have any focus issue. That's a good 1st step. I probably will send this copy back, to get another one. If it's the same, it's probably what to be expected.
03-28-2008, 09:29 AM   #568
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Just today my second DA16-50 came back from Pentax.
It is focussing correct now, at close focus And at infinity!

Relief!

I did a quick test:
This is what my copy looks like at 50mm f2.8
Focussed with AF.
100% crops
(on the left was a bit more daylight, which explains the different colors)
03-28-2008, 09:46 AM   #569
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.

How far away was that chart? I could try some tests with similar sized text at the same distance to see what I get.

I consider my third copy great. There is some corner softness at high apertures, but that makes absolutely no difference to me, and I'm pretty sure it's normal for any good copy of this lens.

From what I've seen, in general, wide angle constant aperture zooms are the most difficult lenses to design - keeping perfect edge sharpness at 16mm while keeping f/2.8 available up to 50mm and distortion low is a tall order for one lens. I'm sure it could be done, but then the 16-50 would be as long as the 50-135 and weigh 50% more, and probably cost $1200.

IMO, A good copy of a 16-50 f/2.8 is a perfect compromise in aspect ratio/length/sharpness/aperture.

With my first copy, it was blurry after almost every AF. I could try focusing out to infinity and back, and then often it was spot-on - unacceptable. My second was much better, but would often hunt more than I thought it should, and still would back focus about 25% of the time.

My third misses the focus about 5-10% of the time, but that could the photographer making mistakes with spot focus on low contrast points... Other than that, it's more than acceptable for sharpness and speed-to-focus.

Under no circumstances did I expect it to maintain edge sharpness like a prime, I think that would be a silly expectation for a sub $800 zoom.

I'd say, if it focuses fast and accurately 90% of the time, and is extremely sharp in the center stopped down and still very sharp wide open, you have a good copy.


.
03-28-2008, 04:54 PM   #570
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That sucks. Who makes that lens for pentax, is it tokina or sigma?
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