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Thread: how to test "sweet spot" of the lens?

  1. #1

    Default how to test "sweet spot" of the lens?

    Hi all,

    As far as I know, "sweet spot" of the lens should refer to the best/sharpness quality you can get from the lens is its focal length + f/stop.

    Care to share with us how to test it out?
    Is the sweet spots varies from camera to camera eventhough using the same lens model/built? or only refer to the lens model itself?

    say, EF-S 18-55mm f/3.5-5.6, EF 50mm f/1.8, Sigma 70-300mm f/4-5.6 APO Super Macro II. what are their sweet spots

    Thanks in advance.

    Cheers!
    Canon 40D|17-55 f/2.8 IS|100 f/2.8 Macro|135 f/2L|300 f/4L IS|430ex|BG-E2

  2. #2

    Default

    Quote Originally Posted by ST_sg
    Hi all,

    As far as I know, "sweet spot" of the lens should refer to the best/sharpness quality you can get from the lens is its focal length + f/stop.

    Care to share with us how to test it out?
    Is the sweet spots varies from camera to camera eventhough using the same lens model/built? or only refer to the lens model itself?

    say, EF-S 18-55mm f/3.5-5.6, EF 50mm f/1.8, Sigma 70-300mm f/4-5.6 APO Super Macro II. what are their sweet spots

    Thanks in advance.

    Cheers!
    The sweet spot depends on the lens not the camera.

    To test the sweet spot (assuming you are using digital camera), take a same picture, preferable in controlled lighting environment, take the picture from from the lowest f/stop to the highest fstop (with relevence to the lighting too, for example if you take f/2.8 at 1/500, then f/4 at 1/250, f/5.6 at 1/125, f/8 at 1/60, f/11 at 1/30, f/16 at 1/15, f/22 at 1/8, f/32 at 1/4) then blow the picture up and see which f/stop give you the sharpest picture with the most contrast, thatis the sweet spot.

    You want to know the sweet spot for your lens, test yourself.

  3. #3

    Default

    I see. Btw, is the focal length a factor for the test?

    say, EFS 18mm f/8 vs EFS 55mm f/8 ?

    Thanks man
    Canon 40D|17-55 f/2.8 IS|100 f/2.8 Macro|135 f/2L|300 f/4L IS|430ex|BG-E2

  4. #4

    Default

    Yes it is....... but I can tell you it normally hover at the mid stop of your lens. If you have a f/2.8 lens the sweet spot will be around f/5.6 - f/11
    Last edited by blurblock; 15th October 2004 at 11:26 AM.

  5. #5

    Default

    For your lenses f8 should be about right. The focal length does matter esp. on your 70-300. It gives the best performance between 100-150. Generally performance is reduced at the extremes of focal length.
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