# Question, Sir/ Madam-600 EX-RT , 90 EX, and ST-E3-RT



## surapon (Mar 28, 2015)

Dear Teachers and Dear Friends.
I do not have Flash 600 EX-RT and ST-E3 RT which use 2.4 GHz RF. to control External New Flash RT system. The QUESTION, Sir, Madam = Do 600 ET RT, 90 EX and ST-E3 RT have Both RF 2.4 GHz and Optical Control in the units to control Old Canon flashes such as 550 EX, 580 EX, 580 EXII-----ETC ?
Thanks you, Sir. Have a great weekend.
Surapon


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## neuroanatomist (Mar 28, 2015)

The ST-E3-RT has only RF control so can only control 600EX-RT flashes. 

The 90EX has only optical control so can control any Canon flash with slave capability (270EX II up to 600EX).

The 600EX-RT has both optical and RF control, but can't use them simultaneously.


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## surapon (Mar 28, 2015)

neuroanatomist said:


> The ST-E3-RT has only RF control so can only control 600EX-RT flashes.
> 
> The 90EX has only optical control so can control any Canon flash with slave capability (270EX II up to 600EX).
> 
> The 600EX-RT has both optical and RF control, but can't use them simultaneously.



Thousand Thanks, Dear Great Teacher Mr. neuroanatomist 
Well, In This Case, I might buy 90EX to use as Master Flash---And I will not bring Heavy Phottix Odin with 4 Receivers Just For when I use only EOS-M, and 2 More Old Canon Flashes 550 EX, and 580 EXII.
Thanks again, Sir.
Have a great Weekend.
Surapon.


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