canon 420ex reduce power output

[heffsarmy]

I was wondering is the a way around reducing the power output of the canon 420ex for high speed photography, to get a flash duration speed of 1/16000, I use two 550ex's but would be handy if I could use the 420ex also...

[heffsarmy]

I had a little think about this and was wondering if I set up a 550ex and 420ex slaves in etl mode, and set the master 550ex on manual mode and reduce its power to 1/32 and leaving all the ratios the same I should be able to get a high speed flash duration of 1/16000 or so on all the flashes??? anyone tried this??? I know that my working range will be only about 2 feet..but would it work

[Jon]

The 420EX won't work if the master's set to Manual mode. If you want to precisely control the duration of the burtst, you need a different flash, or you'll need to do some serious work calculating out how short the burst would need to be for various auto flash ratios and flash-subject distances.

[scottbergerphoto]

You can use the 550EX as a wireless master to manualy control the output of slave flashes. It's in the manual.

[Jon]

But the 420EX manual specifically states that :!:If the master unit's flash mode is set to <M> (manual flash) or <Multi> (stroboscopic flash), the slave units will not fire. Be sure to set the master unit's flash mode to <E-TTL>.