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New Contributor
Posts: 3
Registered: ‎10-22-2015
Accepted Solution

Can I trigger a remote, flash unit from the EOS Utility?

Hello. I am a total newbie, so forgive me if my question is very basic or confused.


I just purchased a Rebel T5i (literally, my first ever SLR purchase) and have been using the EOS Utility to be able to "live view" on my desktop computer screen. This seems to work quite well. 


However, I am interested in adding a remote flash, such as a Speedlite, to place between the subject and a backdrop. Will a remote flash work properly from the EOS Utility live view? Does it have to be a Speedlite, or can it be a third party flash? 


I am not too considered with flash quality as much as I just want to be able to take pictures with the EOS Utility live view, with the remote flash being triggered to light a backdrop behind the subject.



Forum Elite
Posts: 14,025
Registered: ‎12-07-2012

Re: Can I trigger a remote, flash unit from the EOS Utility?

[ Edited ]

In a way the answer is, yes.

But maybe not like you think.  EOSU will controll the T5i and the T5i will control the flash.  You just need a trigger.

IMHO, I would never and I never use anything but Canon flashes.  Whatever the flash must be ETTL compatible.

EOS 1DX and 1D Mk IV and several lenses!
New Contributor
Posts: 3
Registered: ‎10-22-2015

Re: Can I trigger a remote, flash unit from the EOS Utility?



I think I understand what you are saying: The EOS Utility does not communicate directly with the flash; it issues a flash command to the camera, and the camera triggers the flash.


If that is correct, it seems like it would really matter whether the flash was OEM, or not .


I realize, though, that the Canon-branded flashes integrate better in other ways that make them worth the extra cost for many folks.

Esteemed Contributor
Posts: 3,854
Registered: ‎06-11-2013

Re: Can I trigger a remote, flash unit from the EOS Utility?

As Ernie points out... the computer merely tells the camera when to take the shot.  If the camera has a flash, then the camera will trigger the flash when it takes that shot.


But your question is loaded with some nuances and it's not just a straight-forward answer.


A Canon T5i has the ability to remote fire a Canon speedlite if three conditions are true:


1)  The flash must support E-TTL

2)  The flash must support E-TTL "slave" mode (and that mode must be enabled -- it will not be enabled by default.)

3)  You must have a direct "line of sight" between the camera and remote flash.


The camera itself has to be told that it is in a mode where the on-camera pop-up flash will work as a "master" to trigger a remote flash.


But you mentioned that you wanted to place this remote flash between a subject and backdrop -- implying that "line of sight" may not be possible.  That calls for additional gear.


You can learn a tremendous amount about Canon E-TTL flash systems from "The Speedlighter's Handbook" (by Syl Arena) but that book hasn't been updated (so far as I know) to include Canon's new radio-triggered flash systems.  


To do this with Canon gear, you'd want an ST-E3-RT radio transmitter (that mounts to the camera hot-shoe just like a flash) and then use a Canon Speedlight flash with an "RT" suffix such as the Speedlight 600EX-RT (the flagship flash) or the new 430EX III-RT.  All the "RT" products communicate via radio and do not require a direct line-of-sight.


It's also possible to do this with budget gear... you can get a pair of radio trigger transceivers... one goes on-camera and the other goes with the remote flash.  These radio triggers are not "E-TTL" which means the camera and flash will not be able to communicate to negotiate how much power should be used for the shot "on the fly" (as an E-TTL flash can do).  That means you'll have to manually set the power level you want to use.


Having to use manual flash is not to terribly difficult to learn.  The flash and camera wont automatically set your power level as it would for E-TTL flashes.  You control the light by adjusting the power level on the flash (manually) or by moving the flash closer or farther from your subject (or by using light modifiers on the flash) or by adjusting the camera's aperture.


This works well in a "studio" type situation where you can control power settings.  But for "event" photography where you have to shoot on-the-fly and don't get "do-overs" if you botch the shot, you have to learn the flash behavior before you do the shoot. For me, this meant creating a table that shows (for any given power level on the flash) what f-stop I should use at any given flash-to-subject distance.  I typically used non-zoom lenses back in those days but I knew that, for example, a "dance" shot of a couple from waist-up (what we called a "half shot" because we only include the upper-half of our subject's body) was f/16 at ISO 100.  A 3/4 length shot (basically from the knees up) was f/11.  A "full length" shot was f/8, and a group shot might be f/5.6 or even f/4. 


This required some quality time spent testing and filling out such a table.  You wont have time to reference such a table, but I mentally memorized it by distance because subject framing was a good consistent indicator of distance.  (this is a bit trickier with zooms because you can change the subject framing without changing distance.)   But ultimately you end up in a situation where you walk up to a subject at an event, frame the shot, set the f-stop, and capture the image and know that you nailed the exposure even though the entire system is manual.


There are lots of tutorials on how to use manual flash and inexpensive triggers at the Strobist blog (


I use the Canon system.  I use the Canon ST-E3-RT trigger a couple of 600EX-RT speedlights.  The system is rock-solid... it always works. 


Tim Campbell
5D III, 5D IV, 60Da
New Contributor
Posts: 3
Registered: ‎10-22-2015

Re: Can I trigger a remote, flash unit from the EOS Utility?

Thank you for your thorough response!


It looks like I have much to read-up on.

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