pic with new sigma 30-how's it look?

Discussion in 'Lens Lust' started by BellaB, Aug 16, 2008.

  1. BellaB

    BellaB

    90
    May 31, 2008
    Florida,USA
    Yesterday it finally came. My sigma 30 1.4. I almost hugged the UPS guy.
    So I took a few pics with it. Here are two. They were handheld but the cat was still and I used flash. Both are 1/180".
    The first one is f4.8 and the second one f1.4.
    I know I probably have to practice more with it. Especially wide open. But if it has a focusing problem I should see it at f4.8 also, right? So how does it look to you so far?


    trial3009.jpg



    trial4004.jpg
     
  2. First thing that strikes me is that you need to use flourescent or incandescent WB and not Auto in that sort of light.

    Can't comment on the focus, its highly unlikely you'll have a focus problem. Any focus problems are (bluntly) likely to be your fault, not the lens :)

    Once you get used to the shallow DoF things will sharpen up. Focus and re-compose at f/1.4 is pretty hard!
     
  3. BellaB

    BellaB

    90
    May 31, 2008
    Florida,USA
    I didn't worry about WB and that stuff for those shots.
    For the 1.4 I didn't focus and recompose but used the focus points.
    Does the 4.8 look sharp? Would a crop help?
    Am I right to believe that if a lens has a focus problem that it is at all apertures?

    Here is a 100% crop of the f4.8:

    test3crop.jpg
     
  4. pforsell

    pforsell

    Jan 15, 2008
    The answer is yes and no.

    As you close the aperture down the increasing depth of field can mask the focus problem, so the answer is cautious "no".

    Most real world lenses suffer from focus shift, meaning that as you close the aperture down the focusing changes and you'd need to refocus. Unfortunately current lenses and cameras can only be focused with the aperture fully open and that might be incorrect when you press the shutter and the aperture actually closes to the desired setting. So, again another cautious "no".

    If the lens design is perfect (does not have the focus shift phenomenom) and you look carefully (not letting the deeper dof fool you) then yes, the focus problem most likely is evident at all apertures.
     
  5. BellaB

    BellaB

    90
    May 31, 2008
    Florida,USA
    Thanks for your reply. Makes sense. With deeper dof how could you know if the lens focused exactly where you wanted to? Didn't think of that.
    I guess I'll practice some more and also try a few with tripod. I still have a while to return it.
     
  6. Your lens is fine. Ignore all the "you'll need to send it back" stories. Absolute rubbish. Just enjoy your lens.
     
  7. This is a great lens and tend to agree with puddle' but there are some lenses that have just too much problem forum chatter and this is one of them. If you get a good copy it is about as good as you'll get in a fast prime, if not then it's worth sending to Sigma to sort out. The quickest test is to set up three batteries with a 1cm or so space front to back and one side to the other ... then fire off some test shots on a tripod at 1.4 to 8.0 using the centre focus point only and focusing on the central battery. If you ain't got a tripod then you can pretty well forget it. At 1.4 the DOF is so thin that a slight movement will put it off. This lens should be sharp from around 2.0 onwards and certainly usable at 1.4, at least in my experience of the lens.
     
  8. BellaB

    BellaB

    90
    May 31, 2008
    Florida,USA

    Thanks. I'll try that out today.