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auto focus problems with the sigma 30mm 1.4 ?

Discussion in 'Lens Lust' started by BellaB, Aug 5, 2008.

  1. BellaB

    BellaB

    90
    May 31, 2008
    Florida,USA
    I read the reviews on amazon.com and quiet a few explain that this lens has focusing issues and many had to send it back. They also say that it is soft wide open and that it has soft corners at all apertures.
    What are your opinions of this?
    How many of you had to send it back and how many could keep the first one?
     
  2. weiran

    weiran

    966
    Jan 2, 2007
    Nottingham, UK
    Most focus "problems" are user problems, people aren't used to using a lens with such a shallow depth of field. This lens does have fairly soft corners, although that's fine if you're using it as a low light lens wide open, if you want a landscape lens with sharp corners this is the wrong choice.

    I've had two and they've both been fine on my old D80, but at f/1.4 the depth of field is very shallow so it's very sensitive to user error.
     
  3. Phillip Ino

    Phillip Ino

    Nov 26, 2007
    Austin
    What weiran said. Most of the focus issues come from the user and not the lens.
     
  4. I'm happy with mine. At f/1.4, DOF is very shallow. If you AF, lock focus, and recompose, you're almost guaranteed to have bad focus. If you believe you have focusing issues with your lens, set it up on a solid tripod, focus on a static object and evaluate the results. That should eliminate mis-focus due to the user.
     
  5. BellaB

    BellaB

    90
    May 31, 2008
    Florida,USA
    Ok. Thanks for the responses.
     
  6. mikechang

    mikechang

    27
    Jun 9, 2008
    San Diego
    I've seen a few with front or rear focus in other forums
    they were tested like what jemaerca said on a focus chart,
    and was obvious that it does a front or rear focuses a little bit on them.

    but i've never own one myself, can't tell you my personal experience.
     
  7. Aipher

    Aipher Guest

    I didn't have any focus problems at all with mine, and could get accurate focus using any focus point as well (D80). However I stupidly dropped the camera with lens attached and it had to be sent in.

    Now I can't get accurate focus using the top focus point past about 10-15ft, as it tends to backfocus. I really need to send it in again :( 
     
  8. Nuteshack

    Nuteshack Guest

    it's kinda sharp @1.4

    d200
    2585727188_13565af925_o.
    NIKON D200    ---    30mm    f/1.4    1/640s    ISO 100

    d40
    2543047438_97a4679374_o.
    NIKON D40    ---    30mm    f/1.4    1/40s    ISO 200


    just plan on sending it to sigma for a fix....if it so happens u don't need to, consider it a bonus
    ;-)))
     
  9. bill-e

    bill-e

    516
    May 10, 2008
    New Hampshire
    I just bought the lens and was not getting sharp pics wide open so I got another and compared them....exactly the same. It appears the OOF condition in my case was operator error. The DOF is indeed very shallow at 1.4 but whatever you actually focus on is sharp.

    I just snapped a bunch of shots of my granddaughter at 2.8 but alas, I accidentally changed the SD card lock option and I was snapping away with no memory card installed :Angry:. But the other day for another thread I took these two pics to help in the discussion on exactly the same topic. I think they show that my lens is fine and what I've been experience is mostly my noob technique.

    1/3200@f1.4
    1/3200@f2.8
     
    Last edited by a moderator: Aug 6, 2008
  10. bill-e

    bill-e

    516
    May 10, 2008
    New Hampshire
    Amazon is a great place to buy from if you're worried because you can keep getting new lenses until you get the one you're happy with without any hassles. But I don't think you'll need to.
     
  11. BellaB

    BellaB

    90
    May 31, 2008
    Florida,USA
    Thanks nuteshack and Bill for those images. I'm 99.9% sure that I'll get the lens. I'm just a very indecisive person. And as soon as I go through with a decision I regret it. I don't want that to be the case this time.
     
  12. bill-e

    bill-e

    516
    May 10, 2008
    New Hampshire
    BellaB,

    I'm still having my issues with people. Here's a couple of my granddaughter I shot today. The first one is just cropped, no other processing. It's 1/200 @2.8. I think it could stand a little sharpening. The second one is 1/500@2.8 and I used Photoshop's Smart Sharpen at 50.

    And again, with Amazon you have at least 30 days to make up your mind so don't worry about regretting the decision.

    DSC_0541.
    NIKON D40    ---    30mm    f/2.8    1/200s    ISO 200


    DSC_0516sm.
    NIKON D40    ---    30mm    f/2.8    1/500s    ISO 200
     
  13. weiran

    weiran

    966
    Jan 2, 2007
    Nottingham, UK
    Bill, is that second photo unprocessed, because your granddaughter's skin tone is very err... dead!
     
  14. tfenne

    tfenne

    125
    Apr 10, 2008
    Cambridge, MA
    I was in that bucket. My copy focused OK right near the minimum focus distance but once you took a few steps back it front focused quite severely. Tested the heck out of it and convinced myself I wasn't the problem (I think it was the first lens I ever bought after my kit lens). I ended up sending it into sigma for calibration. Got it back about a week and a half later and the focus was perfect.

    Don't know how prevalent these problems are vs. operator error, but the short answer is if you want the lens get it and if it does have focus problems just send it to sigma and they'll fix it right up.

    -t
     
  15. bill-e

    bill-e

    516
    May 10, 2008
    New Hampshire
    Weiran, both photos are unprocessed for color not because I like the way they look, but because I was trying to complain a bit about my problem getting people really sharp. Her skin tone looks like neither of those shots.
     
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