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07-08-2012, 02:03 AM   #16
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QuoteOriginally posted by top-quark Quote
Now, I didn't expect extreme sharpness wide open, but I looked at the F4 shot (and an F5.6 shot too) and thought "that looks plain soft to me". To illustrate, here's a 100% crop from the centre of that F4 shot:
I had a secondhand copy of a DA* 16-50mm some time ago and it wasn't this soft at F4 (or even F2.8). Maybe you should try the brick wall shot again with Live View, so that you can be sure that its not because of any front/back focus issues.

07-08-2012, 03:22 AM   #17
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QuoteOriginally posted by NZ_Ross Quote
All the best with M4/3, I hope you really enjoy it.

I am still enjoying my K-5 and lenses immensely, and having an optical finder, and a really responsive camera is a huge plus.

Regards,

Ross
I still like the K5, if I didn't drown it and start thinking of the next step..... :X When I return to APS-C, Pentax will be my first choice!
07-08-2012, 03:39 AM   #18
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Looks like a bad copy to me. I find the corners are really weak at f2.8 and both wide and long end, but center sharpness should stay decent. Certainly by f4, it should be pretty strong.

16mm and f4

07-08-2012, 03:42 AM   #19
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I also got this lens not too long ago and I first thought it was real bad copy, but it seems that it was because of the focus inconsistency with my K-7. With K-5 it got better. Here are my brick wall shots. Those are handheld, SR on and with normal focusing style (autofocus, no Live View) as this is anyway the way I always take pictures. I don't care if the lens performs well with tripod, 2s mirror lockup and MF focusing as that is not the way I use any of my lenses. It should perform well the way I use it. So, here we go

Center crops, 16mm (at 35mm and 50mm the results were bit better but not much)

F2.8


F8


Upper left

F2.8


F8


Lower right

F2.8


F8


Samples could be better with proper AF adjustment, but still those are acceptable to me. Anyways the corner performance at 2.8 is not that important to me as I will anyways stop down to F8 for landscapes. And F2.8 center sharpness can be easily "recovered" with a bit of sharpening. F2.8 corners are that bad that sharpening does not affect those.

unsharpened 2.8


sharpened 2.8


So I will stop worrying about the quality of this lens now as I know how it performs and go shooting with it. For me this is more than enough. I have also Tamron 17-50/2.8 which is more consistent across the frame (better corners in all apertures and bit better at 2.8) but that's about it. Pentax is weather resistant, silent focusing, better built and feels better. And most importantly I like using it more than the Tamron. That's everything that matters for me as a hobbyist. In the end the bit lack of sharpness can be fixed in the post-processing. The fact that you cannot take your camera out of the bag because of little rain cannot.

07-08-2012, 03:49 AM   #20
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More 100% centre crops of effin' brick wall shots, this time three different lenses at the same time with (more or less) the same frame, on a tripod with remotely triggered shutter:

DA* 16-50mm, 35mm, F4:
Name:  BrickWall-2.jpg
Views: 220
Size:  194.3 KB

For comparison, DA 35 limited, F4:
Name:  BrickWall-5.jpg
Views: 200
Size:  232.6 KB

And (the only other zoom lens that I currently own that can do F4), the DA 55-300mm, 55mm, F4:
Name:  BrickWall-7.jpg
Views: 231
Size:  183.5 KB

(Just by the by, the 18-55 was hopeless at 35mm, F4.5).

Maybe I'm getting all bothered over nothing. I've always found the 55-300 to be perfectly acceptable (but it was also a bargain) and the DA* shot looks a lot better.

As for exposure, it looks like it's underexposing at F4 rather than overexposing at F2.8. I'll have to live with it and play with exposure in post.

Another conclusion: the Tamron 17-50mm simply has superb IQ (although others have issues with this one too).

Maybe I should stop shooting my back wall (my neighbours must think I'm bloody mad) and take the 16-50 out and try and enjoy it. Not this afternoon, though: Andy Murray's in the Wimbledon final!

Last edited by top-quark; 07-08-2012 at 04:23 AM.
07-08-2012, 04:35 AM   #21
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QuoteOriginally posted by top-quark Quote
Maybe I should stop shooting my back wall (my neighbours must think I'm bloody mad) and take the 16-50 out and try and enjoy it. Not this afternoon, though: Andy Murray's in the Wimbledon final!
Now you are thinking right.....pop on down to your local Russian Orthodox Cathedral and see what you can get
07-08-2012, 06:53 PM   #22
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I've been on the forum for a couple years now, and I don't know how many times I've seen threads like this pop up when excited buyers are disappointed with their 16-50mm and turn to the forum for help in determining whether they just got a bad copy.

As far as I've been able to tell, it's just not a particularly outstanding lens, optically speaking. Either that, or it suffers from sub-par quality control. If a friend were asking me, I would first recommend the Sigma 17-50mm, and then the Tamron 17-50mm. Or better yet, a Tamron 28-75mm f/2.8 supplemented buy an ultra-wide zoom.

And no offense to the people who are trying to help out by posting images from their 16-50's, but a picture that is reduced to a fraction of its original size isn't all that useful for judging the quality of the lens. I always link to full size pictures when posting examples of how a lens performs.
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