TMR Design wrote in post #11984273
Something still seems wrong with that.
I found a way to determine the light loss.
I shot a gray card and then looked at the percentages in Lightroom and how much of a change in exposure there was as I increased the shutter speed in full stop increments. The flash was set to 1/4 power.
1/500 -2.7 EV
1/1000 -.8 EV
1/2000 -1.0 EV
1/4000 -1.4 EV
1/8000 -.7 EV
That totals -6.6 EV. That makes more sense to me. Does that jive with anyone else's results?
That sounds about right, Robert. According to the SB-900 manual, at 50mm, ISO 100, the GN of the flash (FX format) is 40 m at or below max sync speed.
And with a shutter speed of 1/500 in FP mode, at 50mm, ISO 100, the GN is 18.4 m, which is more than 2 stops but less than 3 stops less than when not in FP mode. And the Ev drops one stop for each stop increase in shutter speed which also jive, roughly, with what you got.