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Flash percentage

Hi Neil

I was watching a video on the sekonic 478 light meter and it gives a flash perecentage reading. Does this relate to the manual power settings on the speedlite such as 1/1 1/2 1/4 etc? If yes, how do you work out what is 20%, 30 % etc




  • TrevTrev Moderator
    With a light meter like the Sekonic (I have the L358) you can read the percentage of what amount of flash is being used compared to the ambient in a ratio of flash power v's ambient.

    Yes, you can only use it with a Manual Mode flash (flash meters cannot correctly read TTL flash since the pre-flash will trigger a reading and if you set that reading it will be grossly under-exposed as the pre-flash is is very small) so you may set an ambient you like, set the flash, and then take a reading of what your Aperture should be, once it equals what you initially set on camera for the ambient, say it was f8.0, you need to power up/down the flash so the meter then reads f8.0.

    After that is done, you then see that ratio percentage of what power the flash is contributing to the ambient, eg: 20%, 30%, and so on.

    If you want it to be equal in the 50% range, you have to then lower the ambient more so the flash contributes more to get correct exposure.

    Generally a good ratio I find is the 20-30% range of flash power compared to the ambient.

    You can get down to a fairly small amount of flash power so it acts like a fill more than dominant, I've had mine down to 5%, just a blip but still contributing to lift especially eye sockets.

    A dark and moody shot would be like the 30% ambient and 70% flash power.

    Entirely up to you of course.

  • if my failing memory serves me correctly I took a workshop and he suggested that flash be around 35%, now these were for outdoor portraits.  Not sure if that % would change for indoor and obviously it depends on what kind of look you are going for.
  • Neil vNNeil vN Administrator
    Which workshop was that?
  • not yours...........sorry................Joe Brady
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