[wiyum]

I appreciate all that are saying that I can expect magic from this lens, but I'm finding some aberrations that certainly seem less than magical. I don't want to get wrapped up in pixel-peeping and I'm not comfortable in this mindset. At the same time, this lens is a considerable investment for me, and if I have a faulty lens (and let us be clear: plenty of those found their way into the marketplace), then I want it replaced.

Just ran another test, this time against my DVD shelf, which provided a text-rich field all in a single plane. The same results were found: at 28mm, the lens was pretty significantly worse in the corners than at 16 or at 50mm. I noticed something else, something that I had seen but had forgotten to mention: at 28mm, I'm getting significant doubling in the corners. Text in the corners is appearing in two places,offset by a decent amount.

I'm calling Pentax tomorrow to see what I need to do, especially since I'm hoping to send off for the rebate this week.

Will

[Substitute]

I am not saying you can expect wonders I am only saying that maybe a live experience would be more useful. Real life shots and not only tests...If you have doubts, send it back!

[PentaxPoke]

I am not saying you can expect wonders I am only saying that maybe a live experience would be more useful. Real life shots and not only tests...If you have doubts, send it back!

How is a shot of his DVD case any less "real life" than a concert where most of the field is black. "Real Life" shots often mask the problem until it is too late, and the lens is out of warantee. Tests like Will did will reveal a problem right away. I think Will's approach is better for determining if a problem exists with the lens.

Will, if you are getting a "doubling" of images at 28mm you must have a defect in the lens. 28mm should be better than both extremes of 16mm and 50mm. I have two zooms that are both significantly cheaper than the DA*16-50 and neither of them have the problem you describe, nor any of the problems I have had with my copies of the lens.

[Substitute]

main difference is what you'll end up doing with those shots: either realize that your lens may be faulty, or do some real life things, sell them, or enjoy them and realize a few weeks later that it's falty.
And return the lens if need be.
As far as I am concerned, I don't have time to make all these tests, I sell pictures and my lens may even be faulty, but I'll find out some day, and I have a year warranty anyway...so I'd rather do the job, make money and enjoy whatever lens I have!

[wiyum]

I've certainly never run a battery of test like this before, but the reputation of this lens' quality control made it seem like a good idea; turns out it was. Once I find that I've got a good lens, it'll go in the bag and only come out to play.

Had I not tested the lens, sure, I'd have a year to find the problem. But wouldn't it be a shame if I found the problem while on vacation next month? Or rather, when I return and look at the photos at full res for the first time?

It might be a pain, but if it means I'll have a tack-sharp lens when I go on vacation, it'll have been a worthwhile pain.

As for your approach, I don't often shoot stills professionally, so I can't really comment. I do shoot a fair amount of film and video stuff though, and if a problem came up with a lens, it'd be my reputation that took the hit. I test every peice of camera equipment on every job. The problems caught ahead of time save too much money in the long run to not be that rigorous about it.

Just a difference in working philosophy, I suppose, but an interesting one.

[Substitute]

"My reputation" is perfectly fine thank you and my philosophy too since I get contracts ;-)
And I keep getting more since I know how to handle my equipment and know for sure that at full aperture in tthe dark, you won't notice a thing as far as distorsion goes.

So I 'd rather keep on trusting my gear, unless it's proved itself totally faulty on the job!
Besides my reputation would be at stakes and I would question my ability to make good shots, if I weren't able to establish a deep interaction with people, nor to get to their "soul", most of the great photographers had not the best lenses, were not technology fans, and most of their shots were technically faulty, but who cares in the end?
As far as vacation goes, I never take any so..........

[Serpiente]

ok before you start bitchfighting

How can I test very quick in the shop if the lense is good? Maybe some criteria are useful..

[jamesm007]

This lens needs to be replace by Pentax with another offering too much damage to its reputation has been done; therefore too many lost sales. I at times want something a bit better than my Sigma 17-70mm, OK the new DA 17-70mm, tests on the other forum say its just a tad better in IQ, if at all, and just not worth it. So I would love the DA*16-50mm weather sealed a bit wider, great IQ if it works well. That will never happen I did try one at my dealer and it was way off, broke really IMO, it did not take one focused pic out of about a dozen or so. I have read of the o-rings coming out and stuff like that. I could just never feel good about my purchase. Maybe that's not the right thing to say. Good luck and hope you get a winner this time.

[little laker]

My eyes hurt just looking at those pic's Pete

is Pentax working on it? I think their testing isnt optimal

It isn't really a Pentax problem, the lens is made by Tokina.
And I don't know why they can't get their butts in gear and solve their quality control issues.
I don't believe that their other lenses have the same faults, so it's most likely a worn out machine on that assembly line or something stupid like that
(I wonder if they make it the Monday after every drinking holiday )

However, since Pentax now knows about the problems they really should do something about it
Tokina doesn't have anything else in that range, however both Sigma and Tamron have good quality lenses which Pentax might be able to build on.

[PentaxPoke]

Are you sure it is made by Tokina laker? I know the Tokina shares the Pentax design, and according to Photozone they cooperated on development, but I read conflicting accounts as to whether or not they are made in the same factory. It would be interesting to know if the Tokina lens has such a persistent QC problem in the Nikon mount.

[little laker]

I can't say positively, however I understand they're made in the same factory.
Plus I understand that there's quality control issues with their own versions.

I just googled

Tokina AT-C 165 Pro problems

and this web page is the second link.
Do the reviews look familiar
They either get a good copy or a bad copy. No in-between.

[wiyum]

What blows me away is the range of problems. It isn't that all of them are decentered, or that all of them have front or back focus problems. Some have one, some have the other, mine produced doubling in the corners at and around 28mm and wider aperture settings. There's no rhyme or reason, and no "one thing" to look for as evidence of a problem.

I'm surprised there hasn't been a recall.

Will

[wiyum]

There's no "very quick" test to be done. The possible problems reported are many, so you've really just got to run a battery of tests. There's no easy answer here.

[aabram]

I'm not starting new thread but add my recent experience here. Having amassed necessary funds I went to camera shop yesterday, secretly hoping to walk away later with 16-60 DA*. Well, it didn't happen. As I was taking test shots in shop I was surprised to see the softness at wide end wide open. For comparison I tested Sigma 18-50 EX f2.8 which was also on display on same subjects with same settings and it beat 16-60 DA* at f2.8 in all focal lengths up to 50. At 50 Pentax was tad sharper, but from 16 to around 28 it was just horr-rrri-ble. I didn't just believe my K10D LCD but I went home, unloaded pics to my computer and duly examined the shots on big screen. It was uniformly softer, not just the edges. Texts on small items that I could clearly read on Sigma shots where pure guesswork on Pentax shots. 16-50 become much better when stepped down, but for me that defeats the point of having f2.8 throughout whole range in the first place. I can live with softness when it is within acceptable limits but this was too much, especially compared to cheaper Sigma next to it. To be fair, one wide open shot was tack sharp with 16-50 too, though I did nothing differently than with other shots. So perhaps it is true, that focusing may be off with K10D, instead of lens being faulty.

Anyway, no 16-50 DA* for me then for a while. I was sceptical at first with all the talk about DA* lemons but apparently old saying "where there's smoke, there's fire" still applies. I have been lucky with my lenses so far and had no problems with any of them but now I'm probably going to wait for next generation or until I get K20D to try again. I think I can wait and not bother with testing truckload of copies to get the perfect one.

[aabram]

How can I test very quick in the shop if the lense is good? Maybe some criteria are useful..

Well, look for scenes that are important to the type of photography you do. If there are bags and bacpacks on display, they usually have fine texture that you can test the sharpness on, there are batteries or memory cards hanging on the wall with all those various coloured multiple size texts and letters which may just be good enough target to test lens sharpnesse of softness from center to corner. There are darker and lighter coloured bags that you can check for focussing speed and sensitivity. There are usually some bright lights and darker corners to fool the metering, lots of reflections to throw autofocus off etc. There are straight lines (shelves, display cases, ceiling junction stripes) to test the distortion. Be creative.