Trivia - there is more than one way to control flash exposure !

Discussion in 'Lounge' started by anonzzz, 9 Jan 2020.

  1. anonzzz

    anonzzz Moderator

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    Let us have a little fun with a simple trivia. Say I have an a7iii (max sync speed 1/250s, base ISO 100 but can go down to ISO 50) and an Off-Camera-Flash with the following settings.

    1/125s @ f/2.8 @ ISO 100 with flash currently at 1/2 power

    I currently have the perfect ambient exposure but my flash is 2 stops too dark. How do I correct it just by changing the settings above? :)
     
    anonzzz, 9 Jan 2020
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  2. Kocaman

    Kocaman Professional

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    What lens do you have? f2.8 zoom or f 1.2/1.4/1.8 primes? That will change your possible options.
     
    Kocaman, 9 Jan 2020
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  3. anonzzz

    anonzzz Moderator

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    Okay, say 1.4 prime. :)
     
    anonzzz, 9 Jan 2020
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  4. Kocaman

    Kocaman Professional

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    Ok right, here goes....

    Current settings: 1/125s @ f/2.8 @ ISO 100 with flash currently at 1/2 power
    Scenario: Correctly exposed ambient but flash exposure 2 stops too dark

    1/250 f2 iso 100 1/1 flash power
    1/250 f2.8 iso 200 1/1 flash power
     
    Kocaman, 9 Jan 2020
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  5. anonzzz

    anonzzz Moderator

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    Thanks @Kocaman ! You nailed it again. In summary, there are also 3 ways to control flash power (just by using the settings alone).

    1) Changing flash power (very obvious)
    2) ISO/Shutter (limited by max sync speed and hand/motion blur)
    3) Aperture/Shutter (limited by max sync speed and how wide the aperture can open)

    I usually max out Option 2 first to maximize my flash power, then Option 1. Again, not normally Option 3 since it changes the artistic nature (bokeh) of the shot. :)
     
    anonzzz, 9 Jan 2020
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  6. Robert

    Robert Apprentice III

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    Distance of flash to target. 2x Distance = -2 Stops
     
    Robert, 9 Jan 2020
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  7. anonzzz

    anonzzz Moderator

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    True, but we are just focusing on just changing the settings here. :)
     
    anonzzz, 9 Jan 2020
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  8. Kocaman

    Kocaman Professional

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    Yep and not changing the quality of light :)
     
    Kocaman, 9 Jan 2020
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