Percentage of fill flash, for TTL too.

[WayneF]

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

 

[ak_]

"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.

 

[WayneF]

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.