<< Only on the 3, 1V, and D30 is the group ratio function supported.
With other E-TTL ("type A") cameras You can still use any
number of E-TTL wireless flashes, but they will all be, effectively,
in "group A." You still have full E-TTL control over this ensemble.
All flashes fire their exposure-determining preflash in unison; the
camera measures the combined exposure from the preflashes;
it calculates the proper exposure flash; it sends this to the attached
master and then out to all the slaves; and then the exposure is made
and all flash units fire at the same commanded intensity relative to
each one's preflash. The intensity control is by way of flash duration
control, but the flash duration is derived within each flash from the
digital command it receives from the camera immediately before
exposure, not determined during exposure. >>
I guess what has me confused is this: You have a 550EX mounted on a macro
bracket just above the 100 mm f2.8 macro to photograph a bug on a leaf and a
420 EX positioned, say, either to the side or to the side and behind the
subject to light the background, they preflash and the camera sets the
exposure. How does it "know" what each flsh is aimed at so that it doesn't
try to increase the 420EX duration in order to provide more light to the bug
and therebye burning out the background or try to better light the background
by increasing the flash duration from the 550EX and therebye burn out the
bug? I can see how if there were ratioing that by ratcheting down the 420 EX
ratio you could provide less light to the background. However, as a slave
the 420 EX, I presume, could not even be ratcheted down by FEC as I would
suspect that the control from the Elan 7 body would just apply to the 550
Master.
>>>>Yes, as long as you use the Off-Camera Shoe Cord 2 (OCSC 2). This is
the one that comes in one piece and has a coiled cord that will stretch
(with some difficulty) to about 6 feet. And it has to be the "2" version.
This proviso applies to the next couple of Q/As, as well.>>>>
Of course, instead of buying the Off Cord Shoe 2 I have the individual Canon
brand components...the shoe mount, connecting cord etc. I read in a
photo.net thread that this will not preserve E-TTL. Is this true...and if so
why would Canon do this to the more expensive of the wired off camera
options? Also, does this mean that if I wanted to use the 550EX as a
wireless master mounted above the lens on a bracket that I would also have to
purchase the Off Camera Shoe Cord 2, in addition to the wired components I
already have...that would really bum me out.
<<<I'm pretty sure the Elan 7 does not have the algorithms to do true
flash group ratioing. (See answer 1, above.) The use of the ST-E2
would not have a bearing.<<<<
Are you absolutely sure about this....from what I have been trying to read
and understand I thought that this was really the purpose of the ST-E2 with
the Elan 7 (as well as controlling more slave flashes).
<<<The ST-E2 does not add any functionality over a master 550EX on
any camera body>>>
Then what would anyone buy one for? Is it just that it allows control of
more flash units as slaves??
I am really pretty confused about all this...both in terms of what various
components could do and wether it will achieve what I would like.
Howard
[EMAIL PROTECTED]
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