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Thread: Need help for inconsistent lens sharpness.

  1. #1

    Default Need help for inconsistent lens sharpness.

    i was setting my Canon 100-400mm lens sharpness to suit my camera in the micro-adjustment function at 400mm end.
    and i focus on different item at different distance.
    most of the time it performs best at around +15.
    however,there was an instance that 0 is sharper than the +15.

    anybody can explain why is this so?

  2. #2
    Moderator Octarine's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    Something to read:
    LensRentals.com - Notes on Lens and Camera Variation
    LensRentals.com - The Limits of Variation
    Drop the idea that your camera and lens will perform each AF operation in exactly the same way. You actually figured it already with your setup
    EOS

  3. #3
    Moderator Octarine's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    Something to read:
    LensRentals.com - Notes on Lens and Camera Variation
    LensRentals.com - The Limits of Variation
    Drop the idea that your camera and lens will perform each AF operation in exactly the same way. You actually figured it already with your setup
    EOS

  4. #4

    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by Octarine View Post
    Something to read:
    LensRentals.com - Notes on Lens and Camera Variation
    LensRentals.com - The Limits of Variation
    Drop the idea that your camera and lens will perform each AF operation in exactly the same way. You actually figured it already with your setup

    Hmm..interesting articles which i had always suspected that AF is not always accurate and lens/body performance differs accordingly.
    so how should i adjust the camera to get the best result from the lens?
    if i choose either 0 or +15, they will be either sharp or soft and vice versa.quite noticeable difference.

  5. #5
    Member Kenneth67C's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by Turbonetics View Post
    Hmm..interesting articles which i had always suspected that AF is not always accurate and lens/body performance differs accordingly.
    so how should i adjust the camera to get the best result from the lens?
    if i choose either 0 or +15, they will be either sharp or soft and vice versa.quite noticeable difference.
    Did you use a tripod for your test and switch off IS?
    An artist who realizes there is a supreme force and works gladly as an apprentice under heaven.

  6. #6

    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by Kenneth67C View Post
    Did you use a tripod for your test and switch off IS?
    yes.definitely.

  7. #7
    Member Kenneth67C's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    You mention there is an instance when its not sharp.
    Exactly under what conditions is this the case?
    Can you post both pics here?
    An artist who realizes there is a supreme force and works gladly as an apprentice under heaven.

  8. #8
    Moderator daredevil123's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    Please also note that when testing AF, you need to do it in good light. And that means no florescent lights also. If have to test in less than stella light, use a flash when testing.

  9. #9

    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by Kenneth67C View Post
    You mention there is an instance when its not sharp.
    Exactly under what conditions is this the case?
    Can you post both pics here?

    i set up everything inside my house with minimal wind.basically i used AF to lock focus then switch to MF and 10X live view to make sure things ain't too shaky before i snapped.
    it was bright daylight.
    i shot at the bus service board opposite my flat,flat unit number opposite my block(about 200M) car number plate parked opposite my block and block number opposite my block.
    i already deleted all the photos as i roughly know how my lens and camera performs then.
    all the shots are sharp at +15 except for the block number which is sharp at 0.
    all shots are across the road being the bus stop service board the nearest and the unit number the furthest.
    and also did a couple of shots to verify for all scenarios.
    Last edited by Turbonetics; 7th March 2013 at 05:55 PM.

  10. #10
    Moderator daredevil123's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by Turbonetics View Post
    i shot at the bus service board opposite my flat,flat unit number opposite my block(about 200M) car number plate parked opposite my block and block number opposite my block.
    That is not how you tune AF. Use a focus test chart.

    Read the instructions in this site:
    http://regex.info/blog/photo-tech/focus-chart
    Last edited by daredevil123; 8th March 2013 at 02:18 AM.

  11. #11

    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by daredevil123 View Post
    That is not how you tune AF. Use a focus test chart.

    Read the instructions in this site:
    Jeffrey Friedl's Blog Jeffrey’s Autofocus Test Chart

    last time i had printed out the same chart to do it for my standard zoom lens and i wasn't really good at it.
    i will read up this article to extract the correct ways to do it again.
    thanks.

  12. #12
    Moderator daredevil123's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by Turbonetics View Post
    last time i had printed out the same chart to do it for my standard zoom lens and i wasn't really good at it.
    i will read up this article to extract the correct ways to do it again.
    thanks.
    remember to use a tripod. And if light is not good, use a flash.

  13. #13

    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by daredevil123 View Post
    remember to use a tripod. And if light is not good, use a flash.

    sure,i will use tripod especially for such telephoto lens.
    for the flash do u mean speedlites or flashlight shining on the chart?

  14. #14
    Moderator daredevil123's Avatar
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    Default Re: Need help for inconsistent lens sharpness.

    Quote Originally Posted by Turbonetics View Post
    sure,i will use tripod especially for such telephoto lens.
    for the flash do u mean speedlites or flashlight shining on the chart?
    speedlite will do.

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