I wanted to do some additional testing with my 600EX-RTs to find out just how well they will work for fill flash with the subject in shadow and the background sunlit. More or less a normal wedding day situation. 🙂
I also wanted to see what the impact of F stop would have on the background; a line of trees about 40 ft behind the subject. And I got the additional benefit of seeing how good the off center zone focus capabilities of the 5D3 will be capturing focus since I was the only subject available. (So bear with the self portrait examples. 🙂 )
5D3 with 85mm F1.2L II on a tripod about 8 ft from subject. I set the AF to lowest right using the zone capability. That showed there were 4 AF segments active.
The camera was set to Av, ISO 50, -1 EV exposure compensation, metering is evaluative.
Flash was on a stand about 4 ft from subject camera left and looking down about 45* through a Westcott 32″ collapsible umbrella. Flash was ETTL with HSS activated and no flash exposure compensation.
The focus at F1.4 isn’t precise because of the hit or miss nature of a self portrait.
This is at F4.0, 1/800;
and this is F8.0, 1/100; Here the forehead reading was about 1/2 stop hot. Pulling exposure down -.5 brought the forehead reading to within 2 %. All the shots with shutter speeds above sync speed had readings within about 2% of each other.
This was accomplished with the 600EX-RT, realistically the same results would occur with a 580EX or 580EXII, or a Nissin Di866 etc.