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08-30-2010, 01:27 PM   #1
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16-50mm f2.8 qc

Hi Pentaxians,

I absolutely love my K7 and it feels so right with the 16-50 F2.8. You can therefore understand my disappointment when discovering that the centre image is "tack sharp" and yet the edges are soft at F5.6. My lens is 9028368.

Does the lens serial number indicate when the lens was made ?

Any idea how many lenses are affected ?

Please let me know.

Many thanks.

Adam.

08-30-2010, 01:33 PM   #2
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I dont own the lens, but I dont know if this is really QC related. This seemed to be one of the results that Photozone also found:
Pentax SMC DA* 16-50mm f/2.8 ED [IF] SDM - Review / Test Report - Sample Images & Verdict
Looks like in their tests borders start to catch up to the center at about F8
08-30-2010, 02:14 PM   #3
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Adam,
what focal length are you 'testing' your lens at and finding this edge softness?
Have you considered the plane of focus perhaps not being consistent?
08-30-2010, 04:59 PM   #4
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QuoteOriginally posted by Adam Lucas Quote
Any idea how many lenses are affected ?
.
All of them are. Few, if any, wide to short telephoto zoom lenses are sharp in the corner one or two stops from wide open.

08-30-2010, 07:13 PM   #5
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QuoteOriginally posted by Pål Jensen Quote
All of them are. Few, if any, wide to short telephoto zoom lenses are sharp in the corner one or two stops from wide open.
I can name one that is: Tamron 17-50. Even at f/2.8 it is sharp in the corners. Photozone tests (Tamron tests in the Photozone Nikon DX page) prove this out if you dont want to take my word for it (I owned both and posted 2 comparison threads here.) At 50mm, I'll bet the Tamron at f/2.8 has better edge sharpness than the DA* 16-50 at f/5.6.

I would only recommend the DA* 16-50 to someone if I was playing a practical joke on them. The lens is fine if you want to just do portraits so you don't care about edge sharpness or AF speed. Don't know why it needs to be weathersealed though, unless you are doing portraits in the rain.

Last edited by PentaxPoke; 08-30-2010 at 07:20 PM.
08-30-2010, 10:45 PM   #6
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QuoteOriginally posted by PentaxPoke Quote
I would only recommend the DA* 16-50 to someone if I was playing a practical joke on them. The lens is fine if you want to just do portraits so you don't care about edge sharpness or AF speed. Don't know why it needs to be weathersealed though, unless you are doing portraits in the rain.
This is a harsh assessment IMO - but I appreciate where you're coming from and your own experience with the lens.

The copy I had didn't have any appreciable edge softness when stopped down. I'd be surprised if even lab tests could adequately assess corner sharpness at f/2.8 or f/4 because of such thin DoF and the difficulty in providing a subject at exactly equal distance from the lens at all parts seen within the frame.
09-02-2010, 07:52 PM - 1 Like   #7
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QuoteOriginally posted by Ash Quote
This is a harsh assessment IMO
I suspect there is someone else that may have the same assessment: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/112770-da%2A16...ad-dollar.html




"DA*...Where the * stands for: beware!"
09-02-2010, 10:29 PM   #8
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On account of total numbers, as has been discussed in a few related threads, I won't totally discard the virtue of the lens even if for a 5-20% SDM failure rate (if any part of that range is at all accurate worldwide...)

I definitely don't defend the lens's shortcomings - to me they were clear in the AF locking and speed aspects, but let's face it - the IQ of the lens is simply unrivalled. I've tried the Tamron 17-50, and whilst it's the closest contender, it still doesn't have the 'soul' of the DA* - but then again, who wants an optically top quality MF zoom lens? It's a lucky dip - and I was lucky for the duration I owned the lens. Your point is taken...

09-03-2010, 01:48 AM   #9
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From the photos on here this lens is definitely on my to-buy list, even considering all the problems. How does it compare to the expensive Canikon 17-55mm lenses?
09-03-2010, 04:16 AM   #10
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"were clear in the AF locking and speed aspects,"
I am not seeing any problems with AF. It is fast and no hunting, even in difficult situations.

F4, 0,6 sec. ISO 1600. AF integration time 250ms.(if that means anything).
Center spot and hand held in poor lighting. Me thinks the lens is doing very well. At least on the K7.

The edge sharpness could be better but is not noticeably soft in normal everyday shooting.

Last edited by Ex Finn.; 11-11-2014 at 05:51 PM.
09-03-2010, 04:29 AM   #11
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QuoteOriginally posted by Ex Finn. Quote
"were clear in the AF locking and speed aspects,"
I am not seeing any problems with AF. It is fast and no hunting, even in difficult situations.

F4, 0,6 sec. ISO 1600. AF integration time 250ms.(if that means anything).
Center spot and hand held in poor lighting. Me thinks the lens is doing very well. At least on the K7.
The 16-50 does seem to perform better (from an auto focus standpoint) on the K7 than it does on my K20. If you can find a little bit of contrast, it locks pretty quickly. I really like the images I get from this lens, but I would hope that Pentax introduces a version II at some point that improves on the deficiencies.

I don't shoot at 16mm and f2.8 because I do feel like the lens is soft there, but stop down to f4, or move in to 18mm and all of the issues go away.
09-03-2010, 07:24 AM   #12
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QuoteQuote:
Pentax Poke: I can name one that is: Tamron 17-50. Even at f/2.8 it is sharp in the corners. Photozone tests (Tamron tests in the Photozone Nikon DX page) prove this out if you dont want to take my word for it (I owned both and posted 2 comparison threads here.) At 50mm, I'll bet the Tamron at f/2.8 has better edge sharpness than the DA* 16-50 at f/5.6.
I agree with your assessment of the Tamron 17-50mm 2.8. I have shot with it & the K20d since it was released over 2 and a half years ago. It is a great lens, & maintains sharpness to the corners wide open.

I think many people would be very surprised if they compared the rest of the numbers for these two lenses as well.
09-03-2010, 01:45 PM   #13
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Oh , forgot that it is weather sealed, is there anything else in the 16-50 range that is sealed also? Not considering the WR kit.
09-03-2010, 05:29 PM   #14
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QuoteOriginally posted by Ex Finn. Quote
F4, 0,6 sec. ISO 1600. AF integration time 250ms.(if that means anything).
Center spot and hand held in poor lighting. Me thinks the lens is doing very well. At least on the K7.
That one looks about 2 stops under from here...
09-03-2010, 06:58 PM   #15
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QuoteOriginally posted by SpecialK Quote
That one looks about 2 stops under from here...
But of-course it looks like couple stops under, because it is! It was shot with a PENTAX.
All the recorded detail is there if one cares to look for it.
Pardon the terrible sensor noise..
BTW, when I took this, all I could see was pretty much nothing more than a dark shape. Histogram to hell, the first image actually looks like the real deal that I saw.

And on top of all, it was shot in JPEG.

Cheers, Mike.

Last edited by Ex Finn.; 11-11-2014 at 05:51 PM.
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