Control of 420ex slave from 550ex

[Trojandog]

I have a 420ex and a 550ex flashgun.

I want to try photographing hummingbirds and freezing the wing movement (wings beat around 75 beats per second!).

I have been swotting up on high speed flash techniques where you set the flash power at 1/32 to give an effective shutter speed of around 1/22,000. I know that I can do this on my 550ex. I also know that there is no manual control on the 420ex. But, I can use the 420 as a slave from the 550.

My question is:

If I set the 550 on my hotshoe at power of 1/32, will the 420 as a slave also fire at this power? ie.. Does the power set on the 550 transmit to the 420 and adjust the 420 output?

If not, is my only option to ditch the 420 and buy another 550?

Grateful for any advice.
Thanks.

[apersson850]

I don't know for sure with these older flash units, but if I use my 580 EX II units in the same way, one as a master and another as a slave, then yes, the power setting will be sent to the slave.
I can also have different power ratios sent, if the slave belongs to another slave group than group A (the master is alway in group A).

But the 580 EX II obviously has a manual mode by itself, so...

Try it! If you change the power setting on the master from 1/2 to 1/64 or something, you must be able to see the difference by just looking at the slave when you shoot a picture. If there is no difference, then it doesn't work.

[rudy_216]

The 420EX can only work in TTL mode with Canon wireless. It will not slave in manual. God knows why.