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Thread: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

  1. #21
    Member
    Join Date
    May 2007
    Location
    Florida
    Posts
    1,984

    Default Re: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

    All this talk about problems with the DA*16-50 got my hands itchy and I did my first newspaper test ever in my life... The result was positive: accurate focusing, ok sharpness and soft corners at f2.8, possibly minor decentering, everything and everywhere sharp beyond the resolving capacity of my K100D at f5.6 and f8. AFAIK, this is normal for a good copy. The minor decentering may or may not be due to me not having positioned the camera sensor perfectly parallel to the newspaper.

    In fact, as creampuff has mentioned, I wouldn't expect a wide angle f2.8 zoom to have low field curvature, which is basically the cause of corner softness. As far as my understanding goes, the issue of field curvature becomes negligible once the focusing distance is further away. So it's really not a concern unless someone often has to shoot a flat object, face on and close up, with a wide open aperture. Brick walls and newspapers and test charts don't tell you everything.

    I doubt that in terms of IQ the Sigma or Tamron can be noticeably better than the Pentax. If you want 1:3 macro, go for the Sigma. If you want maximum wide angle (I feel that there's a difference between 16mm and 18mm), SDM and weather sealing, treat yourself to the Pentax. If neither appeals to you, there's still Tamron. This is just my perspective on this issue, as I am saying this without having used the Sigma or Tamron before. Everything taken into concern (IQ, build, price, etc), I'm not sure if there's a clear winner among the three.

    Having said that, I also believe that Pentax did have a QC problem with the DA*16-50, otherwise why would we hear so many complains about bad copies of the lens? Some may be just due to unrealistic expectations of the lens, but I remember seeing some pictures from genuinely flawed copies too. The DA*50-135 didn't have such bad rep even though they were released around the same period of time. So I guess it's understandable that people are upset that they have to take their chances with a >S$1000 purchase.

  2. #22

    Default Re: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

    Quote Originally Posted by longko View Post
    ....I think maybe there's some issues with local copies just that nobody really bother send it in. That's unless the copies cubular encountered aren't local either. I mean not everyone will do a full test on the lens, and some just dun use them at f2.8.
    My copy probably isn't local. It was bought from a place which told me "brand new set, but no packaging, and 1 yr shop warranty". I only dared put $ down because they had two copies in equally perfect cosmetic condition, and I needed it rather urgently.
    tHe cUbE

  3. #23

    Default Re: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

    This is a bit late in the day but anyway...

    I got the 1650 with my K-7. Interestingly, I haven't used it much. Till yesterday, when I compared shots with my now-sold E-P1.

    At 50mm, wide-open, the results were soft right across from centre to corner. The situation got better as I stopped-down but this is the first of such problem I've seen in any lens.

    Brought my lens to Emjay's service cubicle today but was told by Kelvin (right spelling?) that there wasn't anything wrong. A little frustrated, I went home and took some more shots around the place and the same thing again. The issue appears only at 2.8 and near infinity.

    I tested my 21mm, 43mm and 50mm and they all checked out fine.

    Since Emjay trawls this forum, what should I do? I am going to shoot some more test pictures at 16mm, 35mm and 50mm, all at 2.8, 5.6 and 8. I am crossing my digits the thing will fail at some point because I don't want a dud when I am away on holiday. Will traipse to the cubicle again tomorrow.

    Anyone else with comments? Ta!

    Grrr...

  4. #24

    Default Re: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

    You can do some AF adjustment and see if it helps.

    I tested a 1650 on my K7, worked ok. But my DA 12-24 needs to adjust AF as much as -10 to make it work well at infinity

  5. #25

    Default Re: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

    Grrr... some more.

    I forgot all about the adjustments! Ha ha!

    Thanks! Will do that before I "stroke" tables.

  6. #26
    Member
    Join Date
    Oct 2002
    Location
    Singapore
    Posts
    171

    Default Re: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

    Emjay's service cubicle? Where is that?

  7. #27

    Default Re: What is it with the Pentax DA* 16-50mm f2.8 ED AL?

    It's in the corridor on the second floor on the side closer to Capitol Theatre and North Bridge Road. #02-32A, I think. It's opposite Cathay's office. It's almost literally a cubicle. When I was there, it as a lone ranger job.

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