Canon ST-E2 question

Ok lets see if I get this right. It can control ONLY 2 groups / or 2 flashes

If you want to have 3 or more speedlights they would needed to be added to either group a or b. The ratio effects the whole group.

i.e group a= 580 Main group b=550 as fill and 550 as hair ration 1:3 so the 2 550 speedlights would be 1/3 power of the 580.

Have I understood this correctly

Just need to check before I buy

I think you've got it there.

yes that is correct.

But you could also set them in manual and control each one by themselves. The ST-E2 will just trigger them.

Sounds about right. Channel C is a background light only, if you point it at your subject they'll be overexposed (unless you use negative FEC perhaps).

You will confuse him with this statements being the St-E2 doesn't have a Channel C.

Group C must be set to manual if trigger from a ST-E2.

Funny I had just re read my 580 and 550 manuals last night and that bit stuck in my head, dont know why but it did.

I also have a couple of Sunpak flashes as well a 455 and 555 tri... whatever that can be fired from the PC cord. The 555 puts out a LOT of light so may use it in a home softbox, its faulty only fires on full power.