ST-E2 Speedlite Transmitter Review

Wireless and Happy!

Peter Kun Frary



The ST-E2 Speedlite Transmitter is a wireless controller and trigger for EX series Speedlites. The wireless possibilities are exciting, especially getting the main flash off the camera. The ST-E2 also sports a powerful near infrared AF assist light, a welcome feature for EOS cameras lacking an AF assist light.

Frary Guitar Duo | EOS 20D, EF 17-40 4L USM, 430EX/420EX & ST-E2

Canon ST-E2 Speedlite Transmitter on EOS Elan 7E

The ST-E2 should be used with an E-TTL capable camera and Speedlite for best results. Older A-TTL cameras, e.g., EOS A2 or 1N, only can only use the ST-E2 in manual flash mode.


The ST-E2 is small and light, tipping the scales at 100 g (3.5 oz) and 62H x 51H x 80D mm. The power source, a 2CR5 lithium battery, is extremely light, especially compared to AA batteries. I can't feel a difference in weight with the ST-E2 attached to a DSLR. Although light, it appears well built, perhaps a little more beefy than the 430EX II Speedlite.

Wittner MT-70 Metronome | Canon EOS 10D, EF 50 2.5 Compact Macro, Manfrotto 190, 420EX triggered by the ST-E2 and bounced off a white panel

AF Assist Light

The ST-E2 is optimized to work with the 45-sensor AF arrays of the EOS 3, 1V and 1D series cameras. Indeed, the AF assist light works perfectly in ECF, manual AF selection and auto AF selection modes with my EOS 3. If you shoot in low available light conditions and have difficulty locking AF, the ST-E2 is an excellent fix (at least within the AF assist beam range). The deep red AF light is discreet—I can hardly see it—and won't offend most subjects.

I tested the ST-E2 on a 5D in a dark room. It projects the entire AF pattern while in auto select AF mode and covers all points. However, when I select individual AF points, it does not project anything for the upper and lower center points of the diamond. It works perfectly for the other 7 AF points, including the far left and right points (will snag AF on a plain white wall). The results are exactly the same on my 20D, 40D, XTi and 5D MKII.

It does an excellent job with the Elan 7E and 10D, but isn't a perfect fit. The AF assist light of the ST-E2 projects a pattern of horizontal lines that cover all 7 AF sensors of the Elan 7 and 10D in auto selection mode. Unfortunately, only the 5 horizontal sensors work with the AF assist beam. Why? The ST-E2 doesn't emit the AF assist light when the top or bottom AF sensors are selected via ECF or manual selection. Perhaps this is because the top and bottom sensors of the Elan 7 and 10D are mainly sensitive to vertical lines and, thus, are unable to achieve AF with a horizontal pattern. However, I don't miss the top and bottom AF sensors much (too many years of using an A2 and EOS 1N).

In low light, I often prefer to AF with the center cross sensor and leave the others off along with ECF. However, I tested the ST-E2 with all 45 AF sensors of the EOS 3 and 7 sensors of the Elan 7E and 10D. In automatic sensor selection mode, I found it locked on to anything in total darkness, even a blank white wall while using a slow zoom. However, the outer edges of the horizontal line pattern are fainter than the middle, leading to focus difficulties with outer AF sensors after 20 feet. However, I can often snag focus with the center cross sensor with objects over forty feet away. The official AF assist range is 34 feet for the center area.

There were no differences in AF speed with the 420EX or ST-E2 attached to my Elan 7E or 10D. However, with the same lens (EF 28-105 USM), center AF sensors selected, my A2 and its built-in AF assist light is slightly faster at focusing. The Elan 7E adjusts AF (rocks back and forth slightly) before locking. The A2 just flies to it and stays.

On the Elan 7E, you may set CF7-3 to disable flash but retain AF assist. On the 10D, set CF5-3 to disable flash but retain AF assist. Unfortunately, the EOS 3, 5D and 5D MK II lack this custom function.

Off-Camera Flash

I walked around with the Elan 7E/ST-E2 in my right hand and the 420EX flash in my left hand and shot party portraits. I could quickly control the angle and height of the flash for more pleasing results than shoe mounting the flash. Also, bouncing off a ceiling or wall was much faster than using the normal tilt and swivel features of the 420EX. Of course, there were no red eye problems whatsoever. For small group shots, I often placed the 420EX 5 or 6 feet to one side (on a stand or held by a volunteer), enough for good modeling and a little bounce off a white wall for fill. I've used similar techniques with the Off Shoe Cord 2 many times, but the ST-E2 is more convenient and flexible. By the way, the ST-E2 works great with the Off Shoe Cord 2 if you need to trigger Speedlites behind your shooting position.

While in slave mode, Speedlites omit near infrared pulses, making them easy to find in the dark!

I shot many small objects with the EOS 3, Elan 7E, 10D, 40D, 5D, 5D MK II, ST-E2 and 420EX/430EX flash with excellent results. For the BG-E4 image below, I placed the 430EX on the floor 5 feet to the right, set the grip on white surface and used a white reflector on the left for fill. I used no compensation and let the Evaluative flash meter do its thing.

Canon BG-E4 Battery Grip | EOS 5D (M mode), EF 24-105 4L IS USM, ST-E2 Speedlite Transmitter, 430EX Speedlite bounced into white panel and Manfrotto 190 Tripod.

I was impressed at how easy it was to set ratios with the ST-E2: enable ratio control and scroll to the desired ratio. Ratios from 8:1 to 1:1 to 1:8 are available for the main and fill Speedlites. The modeling flash, activated with the DOF button on most EOS models, was helpful in selecting the correct ratio. It's easy to burn through a set of flash batteries playing with it!

No Second Curtain Sync

When the 420EX/430EX is shoe mounted or used with the Off Shoe Cord 2, second curtain sync is operational. Unfortunately, second curtain sync is disabled in slave mode (wireless mode) with the ST-E2 and EX Speedlites.

IR Trigger

The IR trigger beam is wide and strong, so line of sight isn't usually necessary indoors. The ST-E2 can trigger the 420EX Speedlite even when facing the the opposite direction (it reflects off nearby surfaces). However, outdoors, or without reflective surfaces, line-of-sight is needed. In the image below, the 420EX was pointed at a reflector on the right side of the ST-E2.

Canon EOS Elan | Photo taken with EOS 5D/24-105 4L IS USM, ST-E2, & 430EX Speedlite bounced into white reflector.


If you need a wireless multiple-flash system for field work, the ST-E2 is an essential tool along with a 430EX or 580EX Speedlite or two. The precision and flexibility of the system beats the tar out of wires and optical slaves. Plus, you also get a wonderful AF assist light to boot.

Canon ST-E2 Speedlite Transmitter on EOS Elan 7E


Type: Clip-on Speedlite transmitter with direct contacts

Compatible Cameras: Type A EOS cameras (E- TTL, autoflash); Type B EOS cameras (Manual flash)

Channels: 4

Flash Ratio Control: For A:B ratio: 1:8 to 8:1, in half- step increments or 13 steps

High- Speed Sync (FP flash): Enabled with high-speed sync mode

Slave Operation Confirmation: With test transmission button. *Slave A fires followed by slave B at 1/64 output.

Flash Exposure Confirmation: Before flash fires during FE lock Adequate flash exposure indicated by the flash exposure level icon lit in the viewfinder. Insufficient flash exposure indicated by the flash exposure level icon blinking in the viewfinder. After flash fires, ST-E2's flash confirmation lamp lights in green for 3 seconds.

Wireless slave SE mode cancellation: Cancels when the test transmission button or FE lock button is pressed to turn on the slave unit.

Wireless Transmission: Infrared pulse

Transmission Range: Indoors: 12-15 meters/39.4 - 49.2 ft; Outdoors: 8-10/ 26.2-32.8 ft

Transmission Coverage: ±40° horizontal and ±30° vertical

Battery Life: Approx. 1,500 transmissions (At room temperature and with a new set of batteries)

AF-assist Beam: Fully compatible with EOS 1V, 3 and 1D's 45-point Area AF and 28mm and longer lens focal lengths. Compatible only with the 5 horizontal AF sensors of the Elan 7E.

AF-assist Beam Effective Range: Approx. 0,6 to 10 m/2.0 to 16.5 ft along the periphery (in total darkness).

SE Feature: While the power switch is set to I or HOLD, the transmission turns off automatically after about 90 seconds of nonuse.

Power Source: 2CR2 lithium (6V) battery x 1

Dimensions: 62 (W) x 51 (H) x 80 (D) mm/2,4 (W) x 3,1 (D) in

Weight: 100 g/ 3.5 oz (excluding battery)

1/8/2002 | Updated 10/13/2014

©Copyright 2002-2017 by Peter Kun Frary | All Rights Reserved


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