Canon Speedlite Transmitter ST-E3-RT Review

Take only what is necessary for radio wireless remote flash and camera control out of the Canon Speedlite 600EX-RT Flash, and what you have left is the Canon Speedlite Transmitter ST-E3-RT. Consuming approximately half of the space of the non-head portion of the 600EX-RT, the ST-E3-RT offers full control of Canon's radio-based wireless system, triggering (or being triggered by) either a flash or a camera.

Wireless flash is often chosen because light coming from an on-camera flash can be less than desirable. Yes, the on-camera flash can be turned off, but the large on-camera flash acting as the master unit is bulky, heavy and thanks to the ST-E3-RT, unnecessary. Another big advantage the ST-E3-RT holds over the 600EX-RT is price – the ST-E3-RT (at review time) costs just over half as much as a 600EX-RT.

Below is a table comparing the size and weight of the 600EX-RT and Speedlite Transmitters.

Model	Weight		Dimensions
Canon Speedlite 600EX-RT Flash	15.0 oz	(425g)	3.1 x 5.6 x 4.9"	(80 x 143 x 125mm)
Canon Speedlite Transmitter ST-E3-RT	3.9 oz	(110g)	2.7 x 2.4 x 3.1"	(67 x 62 x 77mm)
Canon Speedlite Transmitter ST-E2	3.5 oz	(100g)	2.4 x 2.0 x 3.1"	(62 x 51 x 80mm)

For many more comparisons, review the complete Canon Speedlite Transmitter ST-E3-RT Specifications using the site's Flash Spec tool.

The difference that 11 oz (315g) makes in your arms during a long shoot is very big. Remember that these are empty weights – with the ST-E3-RT using 2 AA batteries vs. the 600EX-RT's 4, the ST-E3-RT advantage is even larger than the specs show. The transmitter's significantly smaller size also makes the camera much easier to maneuver – especially in crowds.

Prior to this time, the Canon Speedlite Transmitter ST-E2 included in the comparison was my choice for remotely controlling Canon flashes. I'll talk about and make comparisons with the ST-E2 toward the end of this review.

Here is a visual comparison:

Be sure to mentally remove the shoe stands in the above picture to fully appreciate the size differences (the stands are not included with the transmitters).

Aside from the entire flash lighting capability, the primary features lost by using an ST-E3 instead of a 600EX-RT are:

• Optical wireless control
• AF assist

Otherwise, the similarities are very strong. The back of the ST-E3-RT appears to be lifted right out of a 600EX-RT. I'm going to take the liberty of showing 600EX-RT LCD images below as there was no good reason to spend the time creating news ones. The LCD and buttons are identical and they function identically to the 600EX-RT. The controls are very well laid out and very easy to use. The similarity with the 600EX-RT makes working with Canon's radio wireless system very easy.

If you've read the 600EX-RT review, you are already familiar with the ST-E3-RT. Starting with the power switch, the new settings lock position is included.

Like the 600EX-RT, the ST-E3-RT receives a dynamic 104 x 172-dot LCD display with four buttons below it. These buttons dynamically change their function relevant to the current mode and menu. A large easy-to-reach Mode button and a wireless mode button (used only for Linked Shooting mode selection) just above it conclude the glowing-green button list.

The examples below (again borrowed from the 600EX-RT review) show the modes available on the Canon Speedlite Transmitter ST-E3-RT. Simply press the Mode button to change between modes.

ETTL, M, Multi and Group are the available modes. FEC, FEB, FE-Lock and HS Sync are available – second curtain sync is not.

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Sorry, but I happened to show a 600EX-RT Custom Function that was not available on the ST-E3, but I wanted to give you an example of what the Custom Function and Personal Function menus look like. Tell the flash to increase or decrease its output by using FEC (Flash Exposure Compensation). Tell the flash to produce bracketed output using FEB (Flash Exposure Bracketing) (does anyone use this?). Though flashes do not offer as much power in HS Sync (High Speed Sync) mode, the cameras fastest x-sync shutter speed can far be exceeded in this mode. Second curtain sync is not supported.

The ST-E3-RT has eight custom functions and three personal functions. If you understand the custom and personal functions available, the icons and options in these menus are understandable without a manual.

Here is the list of the 8 Custom Functions found in the Canon Speedlite Transmitter ST-E3-RT:

C.Fn-01: Auto power off (On, Off)
C.Fn-02: Modeling flash (3 button options, off)
C.Fn-03: FEB auto cancel (On, Off)
C.Fn-04: FEB sequence (2 options)
C.Fn-07: Test firing with autoflash (1/32 power, 1/1 power)
C.Fn-13: Flash exposure metering setting (Speedlite button and dial, Speedlite dial only)
C.Fn-20: Beep (Off, On)
C.Fn-22: LCD panel illumination (12 sec., Off, On)

The list of new ST-E3-RT Personal Functions are:

P.Fn-01: LCD panel display contrast (5 levels)
P.Fn-03: LCD panel illumination color: Master (Green, Orange)
P.Fn-04: LCD panel illumination color: Slave (Green, Orange)

Canon EOS digital cameras introduced since 2007 have a flash menu, but you are going to need a post-2011 model to get camera menu support for radio wireless flash control. The 1D X and 5D Mark III are the review-time-available cameras supporting the radio wireless menu. These cameras have a Flash Quick Control screen available for fast, easy setting verification and changes:

Radio Wireless Control

Radio wireless remote control is what the Canon Speedlite Transmitter ST-E3-RT is all about. Unless in Linked Shooting mode, the ST-E3-RT's sole purpose is to act as a radio wireless flash master unit.

Getting your flash off camera opens the door to the more impressive capabilities of flash photography. The ST-E3-RT can control another Canon radio wireless compatible Speedlite with remote slave capabilities – the 600EX-RT only as of review time.

RF wireless is an awesome upgrade from the Canon optical wireless system that I've been using for many years. No longer is line-of-sight and a specific angle-of-view required to control remote slave flashes. No longer do walls, light modifiers or flash angles get in the way of wireless control. Also, remote flashes can be up to twice as far away indoors and three times the rated distance outdoors.

Via 2.4 GHz RF, the Speedlite Transmitter ST-E3-RT is able to control flash output in up to 5 groups (A, B, C, D & E) of up to 15 compatibles flashes (600EX-RT only at review time) communicating in one of 15 channels (default is Auto select) using one of up to 10,000 IDs (default is 0000) from up to 98.4 feet (30m) away. Each group can independently have its mode set to ETTL, M (Manual) or EXT.A (External Auto). Ratios for each group can be set to up to +/-3 stops.

A Link light on the back/top of the ST-E3-RT indicates the ability to communicate with the other flashes using color as follows:

Green: Communication established
Orange: Transmitter has sub-master status (this master unit was powered on after another master unit)
Red: Transmitter is not communicating with another unit
Blinking Red: Too many units or other error

Here is a look at some of the RF identification information/settings on the ST-E3-RT LCD (still, same as the 600EX-RT shown here).

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To insure interference-free communications, the ST-E3-RT has the ability to automatically scan its 15 channels and automatically select the best available. The ST-E3-RT, while manually set to a specific channel number, can produce a chart of the results of its scan as seen in the "Graph" example above. You can utilize this information to manually select the optimal channel for your venue. Obviously, my studio is rather clean from an RF noise perspective.

Bi-directional communications are used in Canon's RF wireless system. One advantage is that the slave flash units report to the master when they are ready and the master can optionally beep to audibly communicate this status the photographer.

As already indicated, radio wireless compatible Canon Speedlite slave units can include, as of review time, only the 600EX-RT. Use the flash specifications tool to check for more recently released flashes. I'm guessing that you will see "-RT" in the name of units containing radio wireless compatibility.

The Canon Speedlite wireless flash system is very easy to use. Insert batteries, lock the transmitter into the camera's hot shoe and power on – the ST-E3-RT is ready to go. For the slave flashes, insert batteries, power the units on, press the wireless button on each flash twice to set slave mode. The RF wireless setup is complete. Everything will work. And it works with great reliability.

The levels of control beyond the simple wireless setup are significant. Here is a look at some of the menus and options:

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Shown in the 600EX-RT images above but not on the ST-E3-RT are the zoom function/display and the flash indicator icon. Otherwise, the two units are the same. The ST-E3-RT lacks the flash on/off function in menu 2. It is always flash-off for transmitters. Menu 3 and 4 are identical.

If you dial in a complex flash setup, you can save it for recall the next time the same situation presents itself – such as the next time you are shooting at the same venue.

Remote Release and Linked Shooting

Not only can the Canon Speedlite Transmitter ST-E3-RT control other Canon Speedlites, but this transmitter can also control other EOS DSLR cameras.

Via its remote shutter release capability, a slave ST-E3-RT can wirelessly instruct a single camera, with another RF-compatible flash or flash transmitter mounted in its hot shoe (limited to 600EX-RT or ST-E3-RT as of review time), to fire in single shot mode. The max range for this function is the same as the other RF wireless features – up to 98.4 feet (30m) away.

The EOS 1D X, 5D Mark III and post-2012-released EOS DSLRs will be triggered directly through the flash hot shoe. Earlier models require the optional Canon SR-N3 Release Cable (shown in use on an EOS 7D below) to function in this way.

The SR-N3 cable requires an N3-type remote release port which leaves some lower end camera models (including the Rebel/***D/****D series) unsupported.

The flash or transmitter on the triggered camera can be instructed to fire or remain off for the exposure and can also control other slave flashes (via RF only). The triggering device is not required to be camera mounted and the ST-E3-RT, with its small size and light weight, is well-suited for this task. The remote release is triggered by pressing the slave's Menu 2 REL button.

Using the Canon Speedlite Transmitter ST-E3-RT's Linked Shooting feature, you really can be in up to 16 places at once. An ST-E3-RT mounted on a camera is able to remotely trigger up to 15 other remote cameras located within the max RF operating range.

When I learned about the new Linked Shooting capabilities, my first thought was to setup a bullet-time-style shoot. Bullet time videos generally utilize a very large bank of cameras, a great deal of wiring and computer triggering technology. A subject in motion is simultaneously captured from many angles using the still cameras. The still images are then incorporated into a video that pans around the frozen-in-time subject.

Wireless triggering technology would eliminate the large wiring and triggering issues involved in such a shoot, but my limited number of fully compatible cameras (3) was going to make my shoot more of a proof-of-concept. What I learned is that there is a very short time lag from the first camera firing until the other cameras fire. This is not surprising, but if the slave cameras are not the same model, there may be a difference in their triggering lag time. My 1D X would trigger slightly faster than my 5D III, but multiple 5D III bodies would fire simultaneously. While more testing is warranted, the bullet time concept has potential. For other remote triggering needs, this system can work very well.

To enter Linked Shooting mode, hold the wireless button in until Linked Shot Slave shows on the LCD. If programming the master flash, press the wireless button one more time. The Linked Shot Master flash triggers the shutter release on the Linked Shot Slave remote cameras. Note that in Linked Shooting, flash information is not communicated to the slave units.

Linked Shooting differs from Remote Release in that the remote shutter activation can be triggered from the master flash camera's shutter release (the REL button also works). Again, Linked Shooting can remotely activate up to 15 cameras whereas Remote Release will activate only one camera.

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As I said before, I much prefer having a Canon Speedlite Transmitter ST-E3-RT on my hot shoe if not using flash on the camera while shooting with wireless flash. The small ST-E3-RT is solidly built. It looks and works great.

The ST-E3-RT battery door is solid and is spring-loaded to remain open while installing batteries. Power is supplies by 2 AA batteries. I strongly recommend using NiMH rechargeable batteries that maintain their charge when on the shelf. I count on Sanyo Eneloop and Sony Cycle Energy batteries.

I'll note here that Canon's previous Speedlite Transmitter, the ST-E2, was powered by a single 2CR5 6v battery. While I don't have anything against the 2CR5 battery, I have nothing else in my possession that uses this battery. I have standardized nearly everything I own on the AA standard (flashlights, smoke detectors, tooth brushes, etc.) and have both NiMH and alkaline varieties charged/stocked for whatever needs them. Eliminating my need for a 2CR5 inventory is a benefit for me.

The back view shows the foot lock and that part is worth talking about. Like the 600EX-RT, the Canon Speedlite Transmitter ST-E3-RT has received a self-cleaning hot shoe foot.

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As we have been seeing on Canon's better flashes, a metal foot provides attachment to the camera hot shoe. But when this transmitter is locked into the hot shoe, it wipes its foot clean. The flash pins swipe across the hot shoe contacts to clean them before realigning into the center of the contacts. This better insures reliable contact with the camera. The switch also auto-adjusts the pressure applied to the pins for an optimal connection.

What you are also seeing in the above image is the hot shoe foot's boot seal lowering into place. This design is similar to the 580EX II, which is designed to seal over the EOS 1D Mark III and later EOS DSLRs. The Canon Speedlite Transmitter ST-E3-RT has, overall, a weather sealed design matching the level of sealing found in the EOS-1D X.

Included with the ST-E3-RT is a nice padded pouch. There are no attachment points/loops on this case, but it easily fits in a pocket or other case.

While the Canon Speedlite Transmitter ST-E3-RT and the EOS 1D X, 5D III and later DSLR cameras are completely compatible, there are some earlier camera model limitations that you should be aware of.

• The flash menu, when available (2007 and later), will not include control of the radio wireless functionality and the Flash Quick Control screen is not available.
• "Wireless flash shooting using the Group flash mode cannot be performed with cameras released up to 2011. Shooting with up to 3 groups (A/B/C) is set." [Canon Owner's Manual]
• With pre-2012 cameras, the optional Release Cable SR-N3 is required for Remote Release and Linked Mode shooting.
• Pre-2012 cameras radio-wirelessly controlling off-camera Speedlites have a max X-sync speed of one stop slower than usual (see owner's manual page 51).
• Radio transmission wireless shooting using E-TTL mode is not possible when using the following list of cameras (note that the 1-series "Mark" cameras are not included in this list):
  EOS-1Ds, EOS-1D, EOS-1V, EOS-3, EOS ELAN II(E)/EOS 50(E), EOS REBEL 2000/EOS 300, EOS REBEL G/EOS 500N, EOS 66/EOS Rebel XS N/EOS 3000 N, EOS IX(E), EOS IX Lite/EOS IX 7.
  Canon recommends shooting in manual or stroboscopic flash modes or to use optical wireless.
• Canon does not recommend radio wireless flash operations with PowerShot cameras.

What are the differences between the ST-E3-RT and the ST-E2

The biggest difference between these two Speedlite transmitters is that ST-E3-RT utilizes radio wireless control while the ST-E2 uses optical wireless control. Which transmitter you need is dependent on what technology your slave units are using. The optical wireless remote technology served me well for a very long time (and this technology remains available in the 600EX-RT), but as I complete this review, I have retired this technology from my use. If you have the choice, RF is definitely what you want.

The ST-E3-RT's advantages over the ST-E2 include:

• Does not have line-of-sight or angle-of-view requirements for both master and slave units
• Transmission range rated up to 98.4' (30m) (vs. up to 39.4-49.2'/12-15m indoors and 26.2-39.4'/8-10m outdoors)
• Remote Release and Linked shooting capabilities
• A more modern design featuring a dynamic 104 x 172-dot LCD display (vs. some lights and LEDs)
• Lock settings position featured on power switch
• 18 custom functions and 7 personal functions (vs. 14 and 0)
• Internal sound generator ("beep")
• Weather sealing
• Self-cleaning hot shoe foot
• Uses two AA batteries (vs. a 2CR5 6v battery)

An advantage that the ST-E2 retains is that it has an AF assist light. The reason this feature was omitted from the ST-E3-RT design is perhaps because Canon's latest high-end DSLR cameras are able to focus in much lower light levels than earlier models. For example, the 1Ds Mark II can autofocus to EV 0, but the 1D X and 5D Mark III can autofocus to EV -2 and the 6D can autofocus to EV -3.

The entire ST-E3 design has been highly modernized, and the ST-E2 appears to have been designed a very long time ago (it actually was). While the ability of the gear to deliver aesthetic images needs to be of primary importance to a photographer, photographers are concerned with the aesthetics of their gear as well. The ST-E3-RT is a winner in this regard.

And it is a winner from a performance perspective. I now have two ST-E3-RT units and six 600EX-RT flashes in my lab/studio/portable kit.

If you are a professional or serious amateur photographer and have the ability to choose the Canon's radio wireless system for your uses, the decision to get one or more ST-E3-RT remote transmitters makes a lot of sense. It costs significantly less than the 600EX-RT, it consumes a fraction of the 600EX-RT's size and it weighs a fraction of the 600EX-RT's weight, but it has all of the 600EX-RT's radio communications capabilities. Free the flashes from your hot shoes, replace them with ST-E3-RTs.