30D with 580EX controlling 420EX

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optimus

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Have been trying out this Master/Slave setup, 580 on the camera, controling the 420 via infra-red.

Just wanted to straighten a few things out, as I have little lighting knowledge, and the ratios have initially been a little confusing for me...

1. I'm pretty sure that I should set the 420 to 'B', so any A:B ratio correspondes to A:580 and B:420. Is this correct?

2. If I set the 420 to 'C', am I correct in thinking that the ratios will effectively be disabled and I can adjust the flash compensation for each unit individually via the 580?

3. When I'm in A:B mode, is any flash compensation dialed into the 580 applied to the 420 equally? Is there any way to adjust them both individually via the 580?

4. What with the 420 being a fully auto flash, am I getting the most control over flash levels by doing everything in ETTL, and playing with ratios and compensation, or is there some other approach? This is for portraiture and I'm thinking about trying AV mode for ambient light, and using both flashes to play around with the lighting.

Thanks in advance for any guidance, I'm new to multiple flashes, so any advice would be appreciated.

Just realised that the 580 will trigger a modelling light on the 420 - had no idea the 420 could do that!
 
optimus said:
[...]

Just realised that the 580 will trigger a modelling light on the 420 - had no idea the 420 could do that!
Click to expand...

Dunno about that "A/B" stuff, optimus, but modelling lights are continuous. The flash from your 420 must have been a measuring flash.
 
I am way open to correction here but I am fairly sure that the ratios only work with flashguns off the camera and a wireless transmitter sitting on the hotshoe.

You would use two oblique lights - left and right.

A would typically be primary and B could be fill from the other side.

C would be to illuminate the background.

Iam now confused myself because the ST-E2 only caters for a and b so not sure how you would control c at the same time...

Any takers - please help!:bonk::thumbs:
 
W.Smith said:
Dunno about that "A/B" stuff, optimus, but modelling lights are continuous. The flash from your 420 must have been a measuring flash.
Click to expand...

It's in the 580ex manual as a 'modelling light' - what's a measuring light?
 
When you have a (late model) Canon flash on the hotshoe it will fire a 1 second strobe burst when you press the DOF preview button.

This called a modelling lamp function and the purpose is to see where shadows would be visible when the flash fires.

It should be used sparingly (cannot remember the exact limits but the manual advises the maximum use per timespan) as it fairly strenuous on the flash.
 
I use a 580 to control a 420 sometimes.
1) forget the modelling light, it is not continuous and looks like a frantic strobe light.
2) I set them both to the same channel. The 580 is in M and then I increase/decrease the exposure as I need to. It seems to tell the 420 to follow suit. I am keen to see how you get on
 
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