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Thread: how to af...

  1. #1

    Default how to af...

    i hav trouble using AF @ night when my subject is standing 2-3m away...how can i avoid this..

  2. #2
    Senior Member giantcanopy's Avatar
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    Default Re: how to af...

    Passive autofocusing that the SLR does obtains information to AF from the image thru the lens, and will be dependent on ambient light presented. The point that you are trying to AF might be too dim / non contrasting for the camera to pick up. Make sure you did not fix any ( circular polarisers ) onto the lens or any teleconverters that might further reduce amount of light entering the camera.

    If you are able to see the item try MF instead. Or get a torchlight to shine on the item and AF, then once obtaining a focus lock, switch to MF and shoot ( but u will probably need some kind of stabilisation such as a tripod )

    Ryan
    Last edited by giantcanopy; 10th August 2008 at 07:45 AM.

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    Senior Member ZerocoolAstra's Avatar
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    Default Re: how to af...

    what camera are you using? I think that all the DSLRs and a number of the prosumers have this AF assist lamp. Subject 2-3m away, should be able to illuminate and get AF lock quite easily and quickly.

    Good luck!

  4. #4

    Default Re: how to af...

    AF at night? Chances are, your subject is not providing enough contrast and your background has more contrast points. Also, you may be using area AF. Try using spot-AF and make sure your subject is selected with one of the AF points. Also, what camera are you using? What lens? If push comes to shove, use MF.
    Alpha

  5. #5

    Default Re: how to af...

    using d40x wif a 55-200 vr lens...yeah it's got the assist light...only dat my subject is wearing a dark coloured outfit...using a torch light yeahh cool...y din i think of dat, i dun really prefer using MF coz the picture on the lcd are decieving it may look crisp...but when u upload ur pics to the pc sumtymes itz blur

  6. #6
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    Default Re: how to af...

    Quote Originally Posted by ary46 View Post
    using d40x wif a 55-200 vr lens...yeah it's got the assist light...only dat my subject is wearing a dark coloured outfit...using a torch light yeahh cool...y din i think of dat, i dun really prefer using MF coz the picture on the lcd are decieving it may look crisp...but when u upload ur pics to the pc sumtymes itz blur
    Please try to put your focus point over an area with sufficient contrast. Camera AF works based on contrast detection.

  7. #7

    Default Re: how to af...

    For Nikon D40x, Popular Photo has a diagram showing the slowing of auto focus speed (0.49s to 1.25s) as light source becomes dimmer. Situation improves when you use a large aperture lens but it won't stop the slowing of auto focus as light gets dimmer.

  8. #8

    Default Re: how to af...

    Quote Originally Posted by ary46 View Post
    i hav trouble using AF @ night when my subject is standing 2-3m away...how can i avoid this..
    by having better light, or manual focusing, or in some cases, like pentax (not sure about other brands), if you pop up your flash, it will send out a short burst of light to light up the area so that af can be achieved.

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    Default Re: how to af...

    Quote Originally Posted by night86mare View Post
    by having better light, or manual focusing, or in some cases, like pentax (not sure about other brands), if you pop up your flash, it will send out a short burst of light to light up the area so that af can be achieved.
    Nikon cameras have a built-in autofocus assist lamp.

    For Canon, you also pop up the flash to emit a short burst of light for AF assist.

  10. #10

    Default Re: how to af...

    Quote Originally Posted by calebk View Post
    Nikon cameras have a built-in autofocus assist lamp.

    For Canon, you also pop up the flash to emit a short burst of light for AF assist.
    It will pop up automatically.

    The downside of the Canon Flash Focus is that whenever i take group shots, i have to tell people that there'll be more than one flash because if not, halfway thru the shot they will move because they assume that the focus flash was the actual flash
    Canon EOS 30D , EF 17-40mm F4L USM , EF-S 55-250mm F/4-5.6 IS

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