Not happy with new lens

Discussion in 'Beyond the Basics' started by scottyb, Mar 19, 2006.

  1. scottyb

    scottyb TPF Noob!

    Joined:
    Jan 11, 2006
    Messages:
    10
    Likes Received:
    0
    I was not thrilled with the "looseness" of the kit lens with my XT. I wanted a better quality general purpose replacement so I bought a Sigma 28-105 2.8-4 DG. I have found that the DOF is very tight and I am having difficulty getting focused shots. When they look good in the viewfinder, the picture is focused slightly off my target. Some pictures have come out really sharp, but many I expect to be good are not. Is this something I just need to become more skilled at, or could the lens be faulty? The kit lens definately has wider DOF across the board.

    Thanks
    Scott
     
  2. 'Daniel'

    'Daniel' TPF Noob!

    Joined:
    Dec 30, 2004
    Messages:
    1,507
    Likes Received:
    14
    Location:
    Manchester, UK
    Are you using manual focus?

    Do you understand about DOF also?
     
  3. scottyb

    scottyb TPF Noob!

    Joined:
    Jan 11, 2006
    Messages:
    10
    Likes Received:
    0
    Yes, and yes. But I am basically still a beginner. The light I had yesterday allowed stops to ~ f10 or so, but those pictures didn't seem to improve the DOF. I think that I just need more time, but it's frustrating.
     
  4. 'Daniel'

    'Daniel' TPF Noob!

    Joined:
    Dec 30, 2004
    Messages:
    1,507
    Likes Received:
    14
    Location:
    Manchester, UK
    Well I can't see it being a problem with the lens because what you see in the viewfinder is what is projected onto the censor.


    Do yuo wear glasses? Maybe you need to change the dioptric setting of the camera so what's in focus to you is really in focus i.e what a 20/20 person would see.
     
  5. scottyb

    scottyb TPF Noob!

    Joined:
    Jan 11, 2006
    Messages:
    10
    Likes Received:
    0
    Funny you mention that as I was just playing with it. I have 20/15 vision. I adjusted the dioptic and I was then able to re-focus and have a clear view, and then again with different adjustments. In other words, I have been able to "correct" the dioptic setting with focus. How can I get the baseline?
     
  6. selmerdave

    selmerdave TPF Noob!

    Joined:
    Nov 30, 2004
    Messages:
    454
    Likes Received:
    1
    Location:
    Brooklyn, NY
    If you're shooting at 28mm with an aperature of f8 with a subject more than 10ft away and you are getting anything out of focus I would say something is wrong. If you are shooting at 105mm all the time unless your subject is very far away you are likely to have much less DOF.

    Dave
     
  7. ChopstickHero

    ChopstickHero TPF Noob!

    Joined:
    Jan 17, 2006
    Messages:
    159
    Likes Received:
    2
    Location:
    Redlands, CA
    can you post up some of the pics you are talking about?
     
  8. LWW

    LWW TPF Noob!

    Joined:
    Aug 3, 2005
    Messages:
    1,206
    Likes Received:
    2
    Location:
    Dayton,Ohio
    I suspect you have the body set to continuous AF and the subject is either moving or you focused on the subject and then recomposed.

    LWW
     

Share This Page