DA* 16-50mm Serial Number Database. - Page 12

bjsmith · 08-16-2008, 06:52 PM

Originally Posted by bjsmith

Defective: 9029210
Purchased DA* 16-50 f/2.8 from Amazon.COM.
Absolutely sharp on the left, very nice, right out to the edges. But about 1/3rd into the right, resolution massively drops off and goes utterly soft.
It's far, far worse than my DA 16-45 f/4 on the right. Horrendously so.

Nominal: 9024998
Replacement DA* 16-50 f/2.8 from Amazon.COM
Not only the right, but even the center, is absolutely sharper than the prior sample.
In my preliminary shots, the very upper left looks a tad softer, but that may be a result of the prior sample being so sharp on the left, possibly inconsistently sharp in the upper left (the prior one possibly favoring it?).
In any case, it's a keeper.

suro · 08-16-2008, 09:37 PM

People, like I guess - do you plan to photograph brick walls and newspapers?

suro · 08-16-2008, 09:44 PM

For most of usual scenes - you not need the sharp edges:

PentaxPoke · 08-16-2008, 11:16 PM

Are you saying that we should just accept a clearly defective lens that costs over $700? And that is a good idea why?

suro · 08-16-2008, 11:47 PM

Originally Posted by PentaxPoke

Are you saying that we should just accept a clearly defective lens that costs over $700? And that is a good idea why?

I bought this lens for the 1200 U$, but it is not important

I think if look defect in each of your lens, at 99% you will find

Some people wrongly testing the lens, or have a problem with the camera AF.

suro · 08-16-2008, 11:56 PM

Maybe this link will help for some tests:

Jeffrey Friedl’s Blog Jeffrey’s Autofocus Test Chart

bjsmith · 08-17-2008, 08:29 AM

Originally Posted by PentaxPoke

Are you saying that we should just accept a clearly defective lens that costs over $700? And that is a good idea why?

Actually, mine cost under US$570 after rebate.

little laker · 08-17-2008, 11:19 AM

Is it just me or does this lens appear to have nothing but good copies for a month or 2, and then a string of duds for a month or 2

2 weeks ago I was thinking that the problems were over (or is it hoping) and now I see that I was wrong

I must admit that I love some of the photographs I've seen taken with it, but at this point I wouldn't even consider asking my camera guy to order one in.
If it was a dud purchased here in Canada I might have a problem trying to get it fixed, or replaced. (Pentax Canada isn't as good as elsewhere)

PentaxPoke · 08-17-2008, 12:12 PM

Originally Posted by suro

Maybe this link will help for some tests:

Jeffrey Friedl’s Blog Jeffrey’s Autofocus Test Chart

Suro,
I think you misunderstand the type of defect people have been having with this lens. A focus test chart like that will not reveal the problem. That is only for determining FF or BF. (BTW, I thought you said people should be taking "usual scenes"

) The problem is with asymmetric focussing across the field of view (decentering), or with doubling or very poor focus at the edges while being sharp in the middle. These have nothing to do with the AF of the camera. They are entirely lens aberrations (defects). I own 8 lenses for Pentax DSLR's, and none of them have had defects except for my DA* 16-50. I have had to send two 16-50's back so far. I posted my latest example here: http://www.pentaxforums.com/forums/p...hapter-ii.html
Those example pictures were perfectly sharp in the center, but the borders were so bad at all apertures, that my cheap P&S looked better than this "premium" lens.

little laker · 08-17-2008, 03:15 PM

The photographs from PentaxPoke's last copy were probably the worst that I've actually seen.

For a moment I actually though it must be something wrong with my eyes, I almost felt dizzy instantly.
Which I didn't think was possible from a photo until then.

suro · 08-17-2008, 08:50 PM

Originally Posted by PentaxPoke

Suro,
IThe problem is with asymmetric focussing across the field of view (decentering), or with doubling or very poor focus at the edges while being sharp in the middle.

Back and front - is one of problems with softer center

Asymmetric focussing across the edges - depends on the size. For crop lenses similar problem as the lens for full frame camera optic (softer edges and vignette). Also, the test must be photographed with a camera tripod and stand on the level (I mean - the wall can be curved, or camera).

P.S. Not sure for my English

PentaxPoke · 08-17-2008, 10:08 PM

Originally Posted by little laker

The photographs from PentaxPoke's last copy were probably the worst that I've actually seen.

For a moment I actually though it must be something wrong with my eyes, I almost felt dizzy instantly.
Which I didn't think was possible from a photo until then.

I was feeling the same thing. I thought it was just due to my anger at having to send yet another DA*16-50 back due to manufacturing defects.

*ve2vfd* · 08-19-2008, 01:03 PM

Originally Posted by little laker

If it was a dud purchased here in Canada I might have a problem trying to get it fixed, or replaced. (Pentax Canada isn't as good as elsewhere)

I've been wanting this lens since the day I bought my first K110.

Now that I can afford it I am terribly hesitant due to that exact reason... Pentax Canada service is awefull (or downright inexistant) and so many duds of that lens are out there. I am not sure I want to take a chance on a $700 lens.

Pat

*sinus007* · 08-19-2008, 01:34 PM

Hi Pat,
You can buy the 16-50 from one of the reputable merchants, e.g B&H, test it and, if it's bad send it back for exchange. You have about 70% probability of getting a good one.
Sorry for bad Pentax service in Canada. I used Pentax USA and didn't have any problems.
As for the lens - like it very much and have a lot of fun.

*nulla* · 08-19-2008, 02:52 PM

I took the plunge and risked buying this lens online from B&H USA as it's price in Aust is far to much.

Despite the posts on bad copies the good reports on this lens outweighed the downside. I received a good lens that has exceeded my expectations

This now is my favourite lens... love it.

Neil