Sigma 10-20 and AF

Discussion in 'Beyond the Basics' started by manaheim, Oct 5, 2008.

  1. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    Has anyone found this lens to be just a hair off when doing autofocus on anything over maybe 20' away? It's not bad, I just find that it's sharper when I just flip it to manual and crank it to infinity.
     
  2. reg

    reg TPF Noob!

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    Never heard of that issue, but my first thought any time I hear of a problem with a Sigma lens is "send it back to Sigma". Seriously, if you're still under warranty, that's just about the easiest thing to do with a Sigma lens with any miscellaneous problem.

    Lucky me that used 18-50 2.8 that I picked up recently is a nice, sharp, WORKING copy, since I can't just send it back to Sigma.
     
  3. dEARlEADER

    dEARlEADER TPF Noob!

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    at 20 feet it should be focusing at infinity.... actually.... anything after 5 or 6 feet with that focal range should be infinity...

    maybe this focus servo is having a hard time deciding a focal point...

    i find autofocus mostly useless on wide lenses anyways.... but if it bothers you.... you can calibrate your D300 to compensate for the difference...


    EDIT: Or... alternatively .. you can return the lens back to the Sigma Lottery Corporation for fine tuning under warranty
     
  4. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    hmmm... I'll have to play with it a bit more. I wasn't aware that it would be focusing to infinity at such a short distance. Not really used to wide angles, which is funny since I use them a lot in the work for my clients. (I just put way more shots through my non-wide angle)

    Are you saying it's common for Sigma lenses to just be off a bit? If so, I guess I could send it in...

    Odd.
     
  5. dEARlEADER

    dEARlEADER TPF Noob!

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    well... i suppose it's common enough that nikon(d300) allows you to compensate each lens for front or back focus.... i think it remembers calibration settings for 10 different lenses of your choice...

    as far a sigma... from my research.... you enter a lottery every time you are buying one of their pieces.... you either get a sharp copy or you get a sloppy copy with variable concerns from poor image quality at wide apertures, focus issues, and/or unusable iq at wide apertures....
     
  6. JerryPH

    JerryPH No longer a newbie, moving up!

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    I own the 10-20 sigma, its bang on for the buck according to my focuschart test.
     
  7. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I've been hearing more and more bad things about Sigma lenses. Of course, people with problems tend to be louder than those who's lenses work fine.

    I can't remember where I read it, but a big lens rental outfit has stopped carrying them because of the initial quality and reliability problems.

    I've got a Sigma 30mm F1.4, which has great optics but doesn't focus accurately.
     
  8. JerryPH

    JerryPH No longer a newbie, moving up!

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    I've heard a lot of bad press in the past about Sigmas, but since last year, they've not been bad at all. I own the 18-50 F/2.8, 30mm F/1.4 and 105mm F/2.8 (oops forgot the 10-20mm Sigma, I own that one too!) and they are all excellent.

    I think it is as is said... the people that complain are heard, but the ones that are satisfied are heard a lot less.
     
    Last edited: Oct 6, 2008
  9. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    I'm going to dig up a focus chart (been meaning to try this anyway) and do some testing with it.

    If it happens that it focuses nearby subjects well and just doesn't do all that well at range it's not a HUGE deal because I'm perfectly happy just plopping it on infinity and leaving it there... I would like to fix it, but I have this odd situation where being without the lens for even a couple weeks would be bad, since I kinda need it for my work. It's pretty amusing, now that I think about it...
     
  10. JerryPH

    JerryPH No longer a newbie, moving up!

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    Here you go, Chris...

    http://focustestchart.com/chart.html

    The PDF file is 16 pages long, but you need print only one page, just follow the instructions to the letter for best results.
     
  11. davebmck

    davebmck TPF Noob!

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    I have the Sigma 10-20 and 18-200 and am very satisfied with both.
     
  12. JerryPH

    JerryPH No longer a newbie, moving up!

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    So, have a chance to do the focus chart test yet? Find anything interesting?
     

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