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  1. #1
    Join Date
    Jun 2008
    Posts
    2,204

    Back focus on Lenses - Tamron 17-50mm and Sony 50mm SAL50-F14

    Ok, so I've tested all my lenses, some many times, and found that the Tamron 17-50mm has back focus (focusing behind the AF point) at 17mm and the Sony SAL-50F14 also has back focus (but more noticeable because it's F/1.4 and at 50mm versus a WA 17mm).

    The Tamron I suppose isn't too affected because at 17mm you wouldn't be using this at its MFD anyway. But it's there nonetheless.

    The Sony is disappointing. It's a brand new lens and would expect Sony to have better quality control.

    Test Setup:

    My very aggressive setup of batteries close together. 1" apart wasn't showing much. Spot Focus, AF on center battery. 2 sec timer on tripod.

    TAMRON 17-50mm F/2.8 (shots at F/2.8)

    above is 17mm showing back focus

    above is 35mm, focus is OK

    above is 50mm, focus is OK



    SONY SAL-50F14


    above is 50mm @f/1.4 showing back focus

    above is 50mm @ F/2 showing back focus


    Question is, what should I do about these two lenses?

    Regarding the Tamron, I think I can live with it unless anyone here things I should send it back to Tamron. It has ~5.5 years of warranty left.

    Regarding the Sony, it's unacceptable and I need to either send it back to JR.com or send it to Sony for servicing (I don't believe I should have to pay for the shipping for their failure, it's brand new).

    I definitely would not send both back at the same time, otherwise I wouldn't have anything to shoot with.

    Could anyone also comment about Tamron and Sony's servicing and turnaround time.
    Last edited by dr4gon; 01-16-2009 at 09:40 AM.
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