From: [EMAIL PROTECTED]
Subject: EOS Canon Wireless Flash
<...>
>If I use a 550EX mounted on the Elan 7 hot shoe I can use the
>550EX with the flash off as a wireless transmitter to an off
>camera 420 EX or I can leave the flash on and use it as a hot
>shoe mounted flash as well as a wireless master to fire an off
>camera 420EX, however, my understanding is that in this mode,
>on the Elan 7, I will not be able to control flash ratios. If this is, in
>fact, the case how does the E-TTL metering work? Will it just stop
>the flashes when the camera detects enough light in total? What
>if I want to use 1 flash on subject and another on the background,
>how does it get balanced?
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.
If you want to balance the exposure differently among flashes using
your Elan 7 (or Elan II or Rebel G or 2000), you have to do it by setting
exposure compensation manually at each flash. Note that this is
possible only with the 550EX; the 420 EX does not have onboard
controls for it.
>Also, can I use the 550EX (if I buy one, I already have a 420EX) off
>camera via a connecting cord and still have it act as a master wireless
>etc as above
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.
>or does removing it from the hot shoe and using a
>connecting cord disable anything (if I use it for macro work I would
>want it off camera)?
No.
> Is it true that if you use a connecting cord with the 420EX you get
>TTL metering but not E-TTL?
I have not heard of this limitation, except with extension cords other
than the OCSC 2.
>If I use an ST-E2 my understanding is I can have a 550EX and a
>420EX off camera and use the ST-E2 to do ratios, even on an Elan 7?
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.
>Is this the only function the ST-E2 adds above using the 550EX in
>wireless mode and how important is this?
The ST-E2 does not add any functionality over a master 550EX on
any camera body.
My $/50.
DGW
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