Hello Danny,

I have the same combination and have also found that it is not possible to
use the 420EX as a wireless slave in the M or MULTI modes. The 420EX
manual states that wireless operation only works for E-TTL (see pages 43
and 48).

Before I would buy another 550EX ($$$), I would consider using neutral
density filters over one of the flash units and/or flash distance
adjustments to achieve a similar effect. I'm assuming that you want to use
manual mode because you want to have a flash ratio greater than 8:1 (or
1:8).

Good Luck!

Dave

"danny" wrote in message
m...
Hi,

Is it possible to set the 550EX in manual mode with a 420EX as a
slave? I've tried the setup in E-TTL mode without any problem but when
the 550EX is set to manual mode, the 420EX is not firing. Am I doing
something wrong or the 420EX is not supported when the 550EX is in
manual and I need another 550EX as slave?