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Thread: Camera Exposure calculations with Flash

  1. #1
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    Arrow Camera Exposure calculations with Flash

    Hi All,

    These days i have been trying my hand on Macro. During by sessions, i came up with some issue in metering. What i'm unable to understand is how to compensate for Flash when using TTL metering. Suppose i'm using Manual mode, and adjust the exposure using camera TTL meter. I take the shot and comes out to be OK ( but the foreground is dark). but when i switch on the flash, it's going to be a bit washed out. My point is if i want to brighten the foreground (meaning thereby i use flash), what should be my exposure compensation on camera so that the foreground is not washed out.


    I know if i switch to Auto mode, i can get something similar to what i wanted in terns of Foreground exposure and details, but my question is how to achieve it in manual mode ( please don't reply by saying just use auto mode).


    It shouldn't matter but just for completing of info, I'm using Canon 40D with 430EX Speedlite.+ Canon 100 mm Macro f2.8.
    Canon 5D mk II /50 f/1.8, 24-105 f/4 IS L, 70-200 f4 IS L, 580EX II
    My Flickr

  2. #2
    Senior Member zac08's Avatar
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    Default Re: Camera Exposure calculations with Flash

    Quote Originally Posted by gumnaam View Post
    Hi All,

    These days i have been trying my hand on Macro. During by sessions, i came up with some issue in metering. What i'm unable to understand is how to compensate for Flash when using TTL metering. Suppose i'm using Manual mode, and adjust the exposure using camera TTL meter. I take the shot and comes out to be OK ( but the foreground is dark). but when i switch on the flash, it's going to be a bit washed out. My point is if i want to brighten the foreground (meaning thereby i use flash), what should be my exposure compensation on camera so that the foreground is not washed out.


    I know if i switch to Auto mode, i can get something similar to what i wanted in terns of Foreground exposure and details, but my question is how to achieve it in manual mode ( please don't reply by saying just use auto mode).


    It shouldn't matter but just for completing of info, I'm using Canon 40D with 430EX Speedlite.+ Canon 100 mm Macro f2.8.
    Use flash ev compensation. Dial in a negative flash ev. This value would depend on how close the subject is and how dark the BG is as the flash will try to compensate for the whole scene.

    It can be from -2/3 to -2.0
    Michael Lim
    My Flickr Site

  3. #3
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    Default Re: Camera Exposure calculations with Flash

    Quote Originally Posted by zac08 View Post
    Use flash ev compensation. Dial in a negative flash ev. This value would depend on how close the subject is and how dark the BG is as the flash will try to compensate for the whole scene.

    It can be from -2/3 to -2.0
    Is this going to have same effect as reducing EV ( TTL meter) on the Camera????
    Canon 5D mk II /50 f/1.8, 24-105 f/4 IS L, 70-200 f4 IS L, 580EX II
    My Flickr

  4. #4

    Default Re: Camera Exposure calculations with Flash

    Quote Originally Posted by gumnaam View Post
    Is this going to have same effect as reducing EV ( TTL meter) on the Camera????
    nope, flash and ambient exposures are 2 different things..

  5. #5
    Senior Member zac08's Avatar
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    Default Re: Camera Exposure calculations with Flash

    Quote Originally Posted by gumnaam View Post
    Is this going to have same effect as reducing EV ( TTL meter) on the Camera????
    Negative. That will be required only if the BG is brighter than the subject.

    I.e. a bird up on a branch in overcast sky as BG. The camera will then meter for the overcast sky and try to brighten up things but will not be able to allow the bird to be exposed clearly.

    I will then try to drop camera EV (again up to situation) and increase the flash ev to about mebbe +1.0 or so to help brighten up the bird.
    Michael Lim
    My Flickr Site

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