17 April 2009

Slave Speedlite tips

430EXIIWhen using the Canon wireless flash system people work in one of two incompatible ways. They put the slaves in manual and set the power on the slaves individually, or they leave the slaves in E-TTL and then use either manual or E-TTL II on the master flash.

If you set the power of the slaves individually in true pure 'strobist' style then you have precise control and can in effect have more than the standard 3 groups of flashes. One flash at 1/128, one at 1/32, one at 1/4 and another at 1/2 power is all possible. Indeed this is the only way to work if you need this level of difference in power outputs. Problem is that to change the power levels you need to go round to each individual slave and make the change.

If you leave the slaves in E-TTL and assign them to the groups A, B and C; then from the on camera master flash such as the Speedlite 550EX, 580EX or 580EX II you determine the settings of each of the flashes in the slave groups. The only important thing is to note or remember which slave is in which group. For ease if you put A slaves to camera left, B slaves to camera right and the C as a background or hair light you don't go far wrong. You can have more than one slave in the same group if needed. 
Put the master flash in manual and then you can set the power level of each A, B and C group of slaves from the master. Leave the master in E-TTL II and use the ratio controls to balance A:B and the flash exposure compensation to adjust the strength of group C. 

In this second approach with the slaves assigned groups and left in E-TTL it makes it possible for a group of photographers to work in either style. The all manual strobist photographer can set the power output for his shots by adapting the power on his master flash, and other photographers can use E-TTL II with ratio control for theirs. Just recently on a model shoot outside we tried exactly this setup, and everyone got the results they needed. The slaves simply take the information from the master that communicated with them last and do what they are told switching from manual power outputs to E-TTL II outputs and even high speed sync as necessary.


-blabpictures-

3 comments:

Simon J said...

Why is it that I can alter the power output from the Master to affect the Slaves in manual mode, yet NOT be able to adjust the exposure compensation from the Master when in E-TTL mode? I have to get up and walk to each flash for this, right?
It beggers belief that all this complex info is being sent wirelessly and I have to actually go to each flash in turn to change the EV when in E-TTL mode.
Unless you know better?
There is a 'wireless set' menu on the camera, but I cannot fathom this at all.....

blabpictures said...

Simon,

The way it works is this - in you're shooting in E-TTL II, then you have ratio control between groups A + B and flash exposure compensation control for Group C rather than having for exposure compensation control for each group.
You can then add exposure compensation control to each flash but this does have to be done manually for each group as you say, or as one over-ride setting from the master flash/camera.
If you want really precise control of each flash group, you are better off going to the manual control and setting them from the wireless flash menu on the camera. Start by setting flash mode to Manual, then go down to Wireless set. You can then enable wireless settings and choose whether the flash on camera fires or not (Master flash... enable/disable). You can then choose the firing groups - if you want three groups and to set the powers independently, go for A:B C. This will allow you to set each power for each group independently below.

Jules said...

Confuses me as well.

Guess I will have to just dive in..

I suppose with "set up" shots its easier to take the time to do this.

I have the ST-E2 trigger gadget, a 430 EX II for ceiling bounce, a 430 EX II into an umbrella and am wondering for portrait shots if I need to experiment with this technique to get a 3rd flash going for the background - to blow it out pure white or for a additional "hair light".

Could that 3rd flash be a small one? Or does it have to be a 430 or 580 to do its wireless 'thing'?