# Percentage of fill flash, for TTL too.



## WayneF (Aug 18, 2015)

We may have heard users of manual flash in daylight speak of metering their fill flash level to contribute 20% or 30% of the total (with ambient).   This is lighting ratio, and it is important, but these percent numbers are about the same as just setting TTL flash compensation to -1 EV or -2 EV fill (there are minor subtle differences, but of course TTL vs manual flash is a big difference too).

If anyone is interested, I added a calculator to compute fill flash percentage of the total light, due to TTL flash compensation (and added some description).  For example, the popular -1.7EV flash compensation is 24% fill flash, which adds 1/3 EV overexposure at the subject.

http://www.scantips.com/lights/flashbasics4.html#percent


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## ak_ (Aug 18, 2015)

"It means sufficient fill flash level to help, but not enough to mess it up, or be identifiable as such."

That's the thing! If it's noticeable, it's a bit too much.


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## WayneF (Aug 18, 2015)

No disagreement, see that same link page, just above the calculator.

But the point was, you can convert TTL flash compensation level to a fill percentage number.


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