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Thread: Test for Back/Front focusing issue before buying lens

  1. #1

    Default Test for Back/Front focusing issue before buying lens

    How do I test the lens that I'm going to buy for front/back focusing issue in the shop?

    Thanks

  2. #2

    Default Re: Test for Back/Front focusing issue before buying lens

    1) download a focus test chart and read how to use it
    2) bring your tripod and laptop as well to the shop
    3) turn off IS/VR (if any) when shooting
    4) view 100% on your laptop

  3. #3
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    Default Re: Test for Back/Front focusing issue before buying lens

    Quote Originally Posted by yc2005 View Post
    4) view 100% on your laptop
    this should be fastest way to test.
    Stirring up emotions with pics - cyliew

  4. #4

    Default Re: Test for Back/Front focusing issue before buying lens

    Quote Originally Posted by yc2005 View Post
    1) download a focus test chart and read how to use it
    2) bring your tripod and laptop as well to the shop
    3) turn off IS/VR (if any) when shooting
    4) view 100% on your laptop
    This is indeed the perfect way to do it...
    But I will not do that, too much hassle and most shops don't like a customer like that.
    Unless you are planning to get a very expensive lens (more then 2k), but again more then 2k lens USUALLY will not have back front focus problem, only the sharpness problem.

    Thus, shoot and view at 100% on a large screen LCD (of camera) is almost good. Test for at least 2 copies, you will be sure of what you get is ok.

    Some shops do allow one to one exchange within 7 days, thus you can test focus problem at home.

  5. #5

    Default Re: Test for Back/Front focusing issue before buying lens

    Change to spot focus, take a pic of remote controls buttons at an angle say 45 degree. Zoom in the preview and see if the number is clear. Unless the button is seriously blur, the issue is minor.

  6. #6

    Default Re: Test for Back/Front focusing issue before buying lens

    i would still print out a focus chart. it beats shooting words on boxes etc. there's no hard and fast rule of doing it.

    what i would suggest is to visit the shop when they are least busy otherwise they tend to get grumpy.

  7. #7
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    Default Re: Test for Back/Front focusing issue before buying lens

    what i do is rest my arms on the table like a tripod...and then shoot words on the box itself. or for the recently acquired 50 f/1.8II, i shot the calculator at an angle. found one copy backfocusing because everytime i shoot a particular button, the one behind it is in focus instead. i think this method words fine enough. what u guys think?

  8. #8
    Moderator Octarine's Avatar
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    Default Re: Test for Back/Front focusing issue before buying lens

    Quote Originally Posted by auden09 View Post
    what i do is rest my arms on the table like a tripod...and then shoot words on the box itself. or for the recently acquired 50 f/1.8II, i shot the calculator at an angle. found one copy backfocusing because everytime i shoot a particular button, the one behind it is in focus instead. i think this method words fine enough. what u guys think?
    Keep in mind that the focus sensor is bigger than the marking in viewfinder. Shooting something where the focus area still has other elements within can result in focus being distracted. The test chart has no other lines, only the single one to be used.
    EOS

  9. #9
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    Default Re: Test for Back/Front focusing issue before buying lens

    Quote Originally Posted by yc2005 View Post
    1) download a focus test chart and read how to use it
    2) bring your tripod and laptop as well to the shop
    3) turn off IS/VR (if any) when shooting
    4) view 100% on your laptop
    I think that is overkill.

    When I got my cheapo tamron 17-50, all I did was the test chart, and the camera body.

    Handheld shot, check on LCD. worked ok. Then again it was a F2.8 lens. If the lens you are testing is not large aperture, will be harder to test too.

  10. #10

    Default Re: Test for Back/Front focusing issue before buying lens

    If your camera has liveview it's very easy to check if it's focusing properly.

  11. #11
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    Default Re: Test for Back/Front focusing issue before buying lens

    ^ I second that. 10x zoom in live view mode is useful for checking focus

  12. #12

    Default Re: Test for Back/Front focusing issue before buying lens

    Quote Originally Posted by Shen siung View Post
    This is indeed the perfect way to do it...
    But I will not do that, too much hassle and most shops don't like a customer like that.
    you are customer.
    Bokelicious Photography : www.bokelicious.net --- Facebook.com/bokelicious

  13. #13

    Default Re: Test for Back/Front focusing issue before buying lens

    Quote Originally Posted by jackzhangxiao View Post
    you are customer.
    YES, but being a not welcome customer will not gain me any advantages. And performing the aforementioned 4 steps is indeed overkill.

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