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Review – YongNuo ST-E2 Wireless Flash Controller

Wireless ETTL Flash Control for Canon – Take your TTL flash photography off the camera

Every digital photography accessory seems to be copied by China manufacturers these days, while most have been shoddy knock-offs that can’t do half of what the original version does, some companies are actually making the effort of improving on the original yet knocking down the price level significantly as well.

The YongNuo ST-E2 is a copy of the aging Canon ST-E2 wireless flash controller that was released way back in 2004-05 era when the Canon 550EX and film EOS cameras were still the bread-and-butter products of Canon. While it was highly revolutionary at that time, it clearly lacks the modern functionalities, flexibility, and usability of the Nikon SU-800 controller. That’s another story to complain about, however.

YongNuo ST-E2 Review

The Canon ST-E2 is an infrared-based flash controller mounted on the camera’s hotshoe that allows the user to control multiple off-camera slave flashes sorted in channels and groups. The ST-E2 allows you to retain ETTL flash metering as well as high-speed sync and ratio-based output even when flashes are placed away from the camera wirelessly.

The YongNuo ST-E2 also sports a high-output auto-focus assist beam to use in low-light, particularly for cameras without a built-in flash/AF assist beam.

The YongNuo variant offers almost identical features, and then some. Here are the key features that the YongNuo have over the Canon ST-E2.

  1. Utilizes 2pcs of standard AA batteries (Canon uses relatively hard-to-find and expensive 2CR5 Li-Ion batteries).
  2. Swiveling head +/- 135-degrees
  3. Significantly increased range, especially outdoors
  4. Metal hotshoe
  5. Price – YongNuo US$106 shipped (eBay) – Canon US$234

The YongNuo ST-E2 works will the Canon 550EX, 430EX (I & II), 580EX (I & II), and other 3rd party flashes that works as a ETTL slave for Canon.

The YongNuo ST-E2, as mentioned, uses IR beams for communication. Unlike radio triggers, the ST-E2 requires line-of-sight for the flashes to receive the signal of the controller. However, line-of-sight is less critical when in an indoor environment as nearby walls and ceilings aid the IR beam patterns even without line-of-sight.

In many cases, manual power flash with radio triggers are more efficient, cheaper, and consistent. However, wireless TTL offers speed and flexibility that may suit event and ‘on-the-go’ photographers more than manual flash adjustment.


The YongNuo (abbreviated to YN, here on-out) ST-E2 package comes with the ST-E2 unit, a stand, velour pouch, a user manual, and a product sheet for other YN products.

YongNuo ST-E2 Review

The YN ST-E2 looks very similar to the original with the exception of a twist-type shoe lock (instead of a locking slide switch) and subtle battery cover door differences.

YongNuo ST-E2 Review

YongNuo ST-E2 Review

YongNuo ST-E2 Review

At the rear, the differences are minimal as well, save for the feel of the buttons and font type.

YongNuo ST-E2 Review

YongNuo ST-E2 Review

The YN ST-E2 sits snugly on a standard Canon hot shoe, no surprises here.


As mentioned previously, the YN ST-E2’s head swivels 135-degrees to both sides. This allows the IR beam to be aimed towards a flash unit better particularly if the flash is off-center.

YongNuo ST-E2 Review

There are no buttons or switches to push when swiveling the head, just a simple twist changes the head direction with a tactile feel every 45-degrees or so.

Range and Sensitivity

I conducted a simple test outdoors with the YN ST-E2 to see how well it works under bright sunlight with direct line-of-sight.


15 Feet


30 Feet


40 Feet


50 Feet


60 Feet


80+ Feet

After 80 feet or so, the flash no longer ‘syncs’ with the shutter. The flash will visibly illuminate during shutter press, but does not register in the photograph. At around 90 feet, the flash no longer fires.

The swivel ability of the YN ST-E2 also allows the user to fire a flash that’s positioned behind the camera, something the Canon version cannot do. The photo below has a 580EX firing through a brolly as fill to the afternoon sun (Group A) while a 550EX placed off to the side as rim light (Group B). The 580EX was placed slightly behind and to the left of camera.

High-speed sync was used to retain f/2.8 aperture for this shot.

2 flashes with HSS

If you are interested in knowing the distance comparison with the Canon ST-E2 as well as multi-flash setup, please check out this Chinese review (you may need Google Translate if you can’t read Chinese characters).

Ratio and Power Adjustment

The ratio works as advertised, but for some strange reason, it didn’t work the first time I tried firing two flashes (A:B), it only fired both flashes at 1:1 ratio.

Nevertheless, everything worked fine a few hours later. The ratio works whether you adjust it via the YN ST-E2 itself or within your camera’s menu system. All of the in-cam “wireless” menu items work with the YN ST-E2.

Flash Off

8:1 Ratio

1:1 Ratio

1:8 Ratio


I advice using full 1.5V batteries for the YN ST-E2 as opposed to 1.2V rechargeable cells. There are reports that the YN ST-E2 doesn’t recycle that quickly as compared to the original, but in my experience, using 1.5V Lithium AA batteries (I use Energizer Lithiums) instead of 1.2V NiMh batteries.

The Canon uses a 6V 2CR5 cell, I would think that dropping the rated voltage to 3V would affect recycling speeds and using even lower 1.2V cells will make things worse.

With fresh Li-Ion AAs, I was able to fire at 8fps consistently as long as the flash itself is up to the task in recycling (full batteries with CP-E4 external battery pack attached).

AF Assist

Using an ST-E2 instead of a full-sized flash for AF-assist purposes is not only lighter, but more compact as well. The full-frame and professional EOS cameras right now lack a built-in pop-up flash that functions as an AF-assist beam as well. With less sensitive AF sensors of non-pro bodies like the EOS 5D and 5D Mark II, the ST-E2 is a good, small, and effective solution in low-light.

Unfortunately, the YongNuo ST-E2 AF assist beam is almost useless compared to the Canon ST-E2 or any other external flash unit’s AF assist beam that Canon offers.

The Canon ST-E2 throws out a matrix-grid like red beam pattern to cover multiple AF points for AF-assist. The YN ST-E2 uses four, VERY thin vertical lines that is not very visible even in pitch-dark rooms, let alone bright enough to help the AF sensors.

Even the pop-up AF-assist light present in consumer-grade EOS bodies, while annoying, do a better job than the YN ST-E2 in this department, which is a big disappointment.

With vertical beam patterns, you need cameras with cross-type AF sensors to even have a chance to using the AF-pattern beam, but most cameras only have vertical AF sensors off-center, so the AF assist beam offers little to no assistance.

The solution could’ve been simple, just change the beam pattern of the AF-assist light. Makes you wonder if they only tested this feature on a 1D series or 7D cameras as these are the only cameras, it seems, that can remotely utilize the poor AF assist feature of the YN ST-E2.

Buy One Now on Amazon


Other than the useless AF-assist, YongNuo seemed to have ticked all the right boxes for a Canon ST-E2 alternative. Better range, swivel head, AA batteries, in-cam menu control, low price. It’s a worthwhile purchase if you like to use wireless ETTL, particularly if you don’t have one of the newer cameras (600D, 60D, and 7D) where there are built-in pop-up flash wireless control.

The price is reasonable for the functionalities as well as the build quality.

Just don’t buy it if you’re looking for a small AF assist beam for your 5D and 1D series camera.

Update, Canon already released the new Canon ST-E3 controller.

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