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Does anyone know if it's possible to use Buff's Cybercommander as a meter instead of the L-358 in the scenario Zenon describes? I'm thinking the Cybercommander can't be set to meter an upcoming flash like the L-358, so it's not as versatile. I didn't see a way in the manual. I ask because I don't have a light meter apart from the Cybercommander and would like to try out Zenon's method with the ST-E3. That method is the way it works with the Einsteins of course.
With my Canon flashes I find it easier and quicker to just set exposure and ratio from the camera via test shots via the clipping warning (for exposure) and visual appearance / left side of histogram (for ratio / full range of detail).
Since exposure definitions and goals vary subjectively I should not my goal is to always capture a full range of detail, at least on the foreground illuminated with the even fill and overlapping key light. That is after all why I go to the trouble of using to flashes.
Only one ratio, regardless how it is set (M or ETTL A:B) or what lights are used will match a full range (black to white) subject to the fixed range of the sensor as in the shot below...
Since camera dynamic ranges differ between brands and models the ratio needed to record the full range varies. With manual flash finding the range is a matter of adjusting fill visually until the files produce the desired shadow detail them adjusting the key light until the files have accurate highlight detail. Then if you have a meter and measure the two lights separately you'd find that the key light is about 1 stop over fill for most DSLRs.
1:1 Even fill
2:0 Key one stop (2x) greater (incident)
3:1 reflected ratio
If you don't have a meter? Set the fill based on visual inspection of shadow detail in the playback then increase key until highlights are 1/3 stop below triggering the clipping warning.
With a pair of Canon flashes in ETTL ratio mode with Master (A by default) as the even fill and Slave (B) as key the process is reversed. First dial in the highlights with FEC to put them 1/3 stop below clipping, then find the A:B ration which puts "normal" looking tone and detail in the shadows. My testing showed A:B = 1:2 does that in most situations. If the room is bouncing a lot of "spill fill" a higher A:B = 1:3 will produce a full range.
The Canon A:B values represent relative INCIDENT strength in the same metering zone. Metering is done by firing a separate pre-flash for A, B, C .... then comparing. So A:B = 1:2 will adjust the power of the "B" slave (regardless of model) is 2x brighter than light hitting a metering zone where "A" fill also hits.
1:1 Group A Master even centered fill
2:0 Group B Slave overlaps and is 2x brighter
3:1 Reflected ratio
So either way it's the same 3:1 reflected ratio that I matching the range of the sensor.
Knowing A:B = 1:2 is full range I use that as my starting ratio baseline. I take a shot, evaluate highlights and adjust FEC to put them 1/3 stop below clipping, then look at the shadow detail and adjust ratio higher/lower as needed. The metering will adjust power so the highlights remain exposed the same.