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Using your flash’s guide number

Started by kgarrison · 11 months ago

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  • Using your flash?s guide number | Camera Dojo...



    What the heck is the GN or Guide Number value when looking at different flash units? The guys at Camera Dojo explain this for you in complete detail....
  • Using your flash?s guide number | Camera Dojo...



    What the heck is the GN or Guide Number value when looking at different flash units? The guys at Camera Dojo explain this for you in complete detail....
  • [...] Kerry of Camera Dojo - ?Using your flash?s guide number? [...]
  • Kerry,



    I'm gonna call you out again. ISO multipliers follow the inverse square law, just like apertures, so the table should read:



    100 - 1.0

    200 - 1.4

    400 - 2.0

    800 - 2.8

    1600 - 4.0

    3200 - 5.6

    6400 - 8.0

    12800 - 11.0 (Only for D3 owners...)

    25600 - 16.0



    Seems much easier to remember, since that same scale is written on my lens and programmed into my camera, and it's correct! Of course, it's not exact, ISO 200's multiplier should really be 1.41421356... but it's close enough.



    Best,

    Tyler
  • Kerry,

    I'm gonna call you out again. ISO multipliers follow the inverse square law, just like apertures, so the table should read:

    100 - 1.0
    200 - 1.4
    400 - 2.0
    800 - 2.8
    1600 - 4.0
    3200 - 5.6
    6400 - 8.0
    12800 - 11.0 (Only for D3 owners...)
    25600 - 16.0

    Seems much easier to remember, since that same scale is written on my lens and programmed into my camera, and it's correct! Of course, it's not exact, ISO 200's multiplier should really be 1.41421356... but it's close enough.

    Best,
    Tyler
  • Hello,

    Thank you for this tutorial.

    But there is something that I do not understand.

    With a Canon 580exII, I have to use 190 or 58 NG in the Calculation Spreadsheet?

    I do not understand the 190 number if the number of guide 580exII is 58?



    Thank you for your reply (I don't speak English very well)
  • Sorry, I understand... it's the metter's convertion ( :
  • Hello,
    Thank you for this tutorial.
    But there is something that I do not understand.
    With a Canon 580exII, I have to use 190 or 58 NG in the Calculation Spreadsheet?
    I do not understand the 190 number if the number of guide 580exII is 58?

    Thank you for your reply (I don't speak English very well)
  • Sorry, I understand... it's the metter's convertion ( :

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