Is my lens to soft? (Pics)

Discussion in 'Digital Photography' started by RedDragon870503, Sep 14, 2009.

  1. RedDragon870503 macrumors 6502

    RedDragon870503

    Joined:
    Sep 6, 2006
    #1
    I bought a Tamron 28-75 f2.8 a while back, I picked the Tamron over equivalent Canon (24-70L) because many reviews claimed it to be sharper... But mostly because it was a third the cost.

    Anyway! I took 4 pictures at f11, f5.6, f4 and f2.8. 11, 5.6, and 4 look fantastic but f2.8 looks horrible. All were tripod shot at a relatively low ISO from a 40D. Then I did a 100% crop

    My question is: is 2.8 bad enough that this might be a bad copy or am I expecting too much.

    http://web.me.com/drewjosephgoede/drewjosephphotography/Photos.html
     
  2. gnd macrumors 6502a

    gnd

    Joined:
    Jun 2, 2008
    Location:
    At my cat's house
    #2
    Usually lenses are at their worst wide open. Also, at f2.8 the depth of field will be the smallest, your blurriness might be caused by not precise enough focus.
    What focal length were you using for these shots? Since what we're looking are 100% crops, what was the focus point? If the focus point was the tip of the nose, at f2.8 the eye will be out of focus.
    Looking at the f2.8 shot, I think the point of focus might be a bit behind the eye, the tops of the eye lashes are already out of focus.
     
  3. RedDragon870503 thread starter macrumors 6502

    RedDragon870503

    Joined:
    Sep 6, 2006
    #3
    These were all shot at 75mm with spot focus on the pupil... I thought that it might be that the DOF is so slim that it was causing the details to be out of focus but after taking 10 or so shots at 2.8 with the same result I figured it was just not sharp at that aperture...

    I know that lenses get less sharp when they are wide open but is this TOO soft?
     
  4. Phrasikleia macrumors 601

    Phrasikleia

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    Feb 24, 2008
    Location:
    Over there------->
    #4
    To be absolutely sure, I'd try again with a stationary subject. A person, and most especially an eye, is not the right subject for this kind of test.
     
  5. RedDragon870503 thread starter macrumors 6502

    RedDragon870503

    Joined:
    Sep 6, 2006
    #5
    That is a good very good point... For arguments sake, lets say I get the same result with a stationary subject. Would you say the lens was too soft?

    BTW, the shutter speed was 1/160.
     
  6. Phrasikleia macrumors 601

    Phrasikleia

    Joined:
    Feb 24, 2008
    Location:
    Over there------->
    #6
    Yes, but this is almost certainly a combination of motion blur and DOF. The skin at bottom left and one of the eyelashes is much sharper than anything else--that's highly unusual for any lens, so it's unlikely to be the fault of the optics. Eyes twitch very quickly, you know, and f/2.8 can produce a very narrow DOF.
     

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