From: [EMAIL PROTECTED]
Subject: Re: EOS Canon Wireless Flash
<<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? >>
It doesn't need to know where each flsh is aimd. (<)B^)). Whatever light
from the entire set of flashes falls on the main subject, plus ambient
light of course, determines (in a mysterious and wonderful way) what
exposure the camera will command. It has three variables it can control:
Aperture, shutter duration, and flash power. It will try to choose a set
of these variables that satisifies main subject exposure (usually
coupled to the focusing point), and secondarily background exposure.
<<I can see how if there were ratioing that by ratcheting down the 420 EX
ratio you could provide less light to the background>>
Good so far.
<<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.>>
FEC from the camera body will affect all flashes, master and slave, alike.
The only problem with the 420 EX as a slave is that there is no way to set
FEC individually at the unit. A slave, if you will, with no mind of its
own.
<<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? >>
The individual extension component set was designed before E-TTL. I
conjecture that they did something in the wiring of the cable set that
allowed
multiple pre-E-TTL tech flashes to be wired 'in parallel,' but when E-TTL
came
along, this design feature made the cable set unable to support it.
<<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.>>
So solly. At least with wireless E-TTL, there's only gonna be one more
cable
to buy, ever. (Well, until they come up with a longer, non-coiled variant
of the
OCSC2.)
<<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).>>
Not "absolutely," only "pretty." Julian Loke suggested the following thread
to
me: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=001QD3
There are contradictory assertions and conjectures there, and I (stubborn
coot that I am) remain unconvinced that the Elan 7 can support multiple
wireless flash groups or that the ST-E2 can do anything the 550EX can't.,
other than make people stare at your camera and say, "whazzat?"). If
the Elan 7 supports multiple groups, one wonders why Canon doesn't
come out and say so, somewhere. One respondent in the above thread
got a reply from Canon customer service that seems to say that it does
not, although the citation is confusingly worded. BTW, the ST-E2 came
out around the time of the 550EX, well before the Elan 7.
<<<The ST-E2 does not add any functionality over a master 550EX on
any camera body>>>
<<Then what would anyone buy one for?>>
Cheaper.
<<Is it just that it allows control of more flash units as slaves??>>
I don't think its signal flash power is any greater than that of the 550EX.
It's too bad that the ST-E2 doesn't support the F.E.C. for group C like the
550EX does; it biases one's purchasing decision in favor of the 550EX.
Then again, I just couldn't justify a fourth 550, so I went with the ST-E2.
I have speculated here in the past that it was a product chronology or
product planning issue at Canon that caused the lack of group C on the
ST-E2. They could've done it with just one more button on the back, plus
of course more firmware inside. Maybe the profit margin is so much
better on 550EXs that they want to sell more of them relative to the
ST-E2s. Then again, maybe they'll come out with an ST-E3.
<<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.>>
Welcome to the club. +=<)B^)
<<I also wanted to ask about the preflash. I have never actually seen the
preflash on my 420 EX go off when I take a photo. Is that because it is so
brief and closely timed to the actual flash that it is not discernable as a
separate event?>>
As Dave Herzstein mentions, you can see the preflash in the viewfinder.
Another neat trick is to set second-curtain sync and a long (say, 1 sec)
exposure. Now the preflash and the exposure flash will be separated
by 1 second.
Hey Canon, you need an E-TTL product design advisor/engineering
consultant! I work cheap, considering how good I am +===<)B^).
DGW
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