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Old Sep 1, 2006, 10:14 PM   #1
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I've seen some people use only 550EX or 580EX speedlites in their wireless setup. I was just curious as what the advantage is for using only one flash model. Is it just to keep a consistant GN? Are there other notable advantages that justifies the cost (instead of getting the 430EX or sigma 500 as slaves)?

Appreciate any comment.
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Old Sep 2, 2006, 10:23 AM   #2
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IMO - No the GN is not critical

I don't have the 580EX yet, but I've been using a 550EX with two 500DG Super interchangeably (i.e. with either the 550EX or the 500DG as the Master)

Remember it's the camera that does the metering and not the flash so even though for example you're doing a 2:1 ratio using 3 flashes: 1 Master on the camera (set to no output) and two slaves for 2:1 ratio, the camera E-TTL (I or II) will meter all three flashes (all with different GN) separately and will command each flash(es) to output their right amount:

Check-out the control timing below (green wireless transmission) - The main final output (big blue) of all flashes (after the metering of each head) individually come last:
-> i.e. there's a wireless control transmission for each pre-flash (blue) firing and their respective metering (purple) !!!





I would put the higher GN flash at the more powerful position though since putting a lower GN will lower the entire system output...

BTW Minolta came out with this system 1st and there's an excellent write-up on this subject, especially the use of ratio or how the wireless system work, which has been around for a while - Highly recommended reading: http://www.friedmanarchives.com/flash.htm
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Old Sep 3, 2006, 1:03 AM   #3
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Thanks for the link, that was very interesting to read. At least now I know Canon's wireless systems has some kind of advantage (that requires either a master flash or a transmitter on the shoe). But the advantage of automatic ratios isn't worth the extra hundreds... at least it feels that way when I know there's a very simple way to calculate ratios without fancy equipment .

But now I definitely feel better about getting a 430EX or sigma 500DGs instead of getting another 1 or 2 580EXs .
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Old Sep 3, 2006, 7:42 AM   #4
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BoYFrMSpC wrote:
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... at least it feels that way when I know there's a very simple way to calculate ratios without fancy equipment .
Very true...

The advantage I see is the freedom to move the head(s) about without having to recalculate each time when you want to be creative - You can also have up to 3 groups of slaves (the math get slightly harder...), each with their own ratio!

BTW all this can be done from the Master flash (i.e. 580EX or 500DG) so you don't have to touch the slave(s) - For example changing from 1:2 to 1:3 (on group B) and 1:4 (on group C) right on the camera!
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