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Thread: AV & TV mode ?

  1. #21
    Moderator catchlights's Avatar
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    Sep 2004
    Punggol, Singapore

    Default Re: AV & TV mode ?

    Quote Originally Posted by Jeremy1 View Post
    Hi, just a bit curious.

    AV - Aperture-Priority
    TV - Shutter-Priority

    As what I know, AV let u adjust the Aperture smaller or bigger & the camera will adjust the shutter speed accordingly whereas TV is the other way round.

    So is there a difference in the picture image taken on this 2 modes ?

    Quote Originally Posted by Jeremy1 View Post
    I did compared AV & TV on bright light still object. No difference.
    I haven't really tried moving object yet.

    In night shot, AV is much prefer as I noticed that the picture look much much better exposed as in TV, it's too dimmed.

    But I rather use manual mode for night shot.
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  2. #22

    Default Re: AV & TV mode ?

    Quote Originally Posted by bengchiat View Post

    maybe i don't know how to communicate properly,
    but whats stopping the user from,

    -using Tv n adjust the shutter to get the aperture u want, or
    -using Av n adjust the aperture to get the speed u want?

    its just a matter of convenience n getting use to it,
    in terms of image produced,
    there shouldn't be any difference.

    1/125 f8 is still 1/125 f8,
    be it Tv, Av or manual(ok, not really for manual, but diff is sml).
    there's some fundamental prob here... when using Tv (shutter priority) u r basically adjusting the shutter u want n letting the body determine the approriate aperture.
    what u r saying is adjusting the shutter in Tv mode such that the body will give u the aperture u want? that's just wrong... similar theory applies to Av mode...

    it's not a mere matter of convinience n getting used to.. it's a matter of practically and needs for the type of picture u want.

  3. #23

    Default Re: AV & TV mode ?

    I think there is some misunderstanding about exposure and effect eg bokeh, trailing, etc

    Exposure is about the brightness of the photo generally affected by shutter speed and aperture. In auto mode, shutter speed change in opposite direction with the aperture.

    Hence if you increase the shutter speed ie from 1/10s (slow) to 1/1000s (fast), the aperture will decrease ie from f/13 to f/4 to get the same exposure (brightness). Generally, increasing one f/stop will decrease one shutter speed. Therefore, if good exposure is obtained with f/4.5 and 1/160s then the same exposure will be obtained with f5 1/125, f8 1/50, f11 1/25, and f/25 1/5.

    However, the effect on the photo will be different. With small aperture f/large number, the depth of field in large (meaning the foreground and background equally sharp) but those with large aperture f/small number, there will be bokeh effect (subject clear, background blur), despite the same exposure (brightness)

    Similarly, if you are taking a moving car, prolonged exposure time (slow shutter speed=1/small number) will give you a trail of light, whereas short exposure time (fast shutter speed=1/large number) will give you a stationary car. And all this will have the same brightness.

    Therefore, when to use Av/Tv will depend on what effect you want, and not the exposure you want.

    This is a brief explanation. If you find this not helpful or need to know more, read up the books recommended by catchlight or any basic photography book from the library.

    P/S: there are other factors, but need to understand this fundamental principle before bringing in the rest.
    Last edited by two200; 19th October 2009 at 12:54 PM.
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