Canon ST-E2
ST-E2 - Features
Ratio buttons not working
Ratio Tutorial
ST-E2 conclusion

Canon ST-E2

The Canon ET-S2 wireless infrared trigger is a light device which can remotely trigger your external Canon Flashlite's. This makes it possible to use your speedlite while it's not physically connected to the camera and thus let the light fall from any side, instead of directly from the front.

. These devices are pretty expensive, and some of the newer Canon aps-c camera's have a flash-master in the built-in flash - so check this before considering an ST-E2! Also note the newer flashes, like the 600RT have a radio-based trigger, as opposed to optical trigger.

ST-E2 Features

  • The ET-S2 supports 4 different channels to avoid interference from other photographers equipment
  • Within this frequency the ST-E2 supports 2 groups (A and B), though not group C (which is supported by the speedlites).
  • You can have multiple speedlite's within a group (each group will be remotely triggered simultaneously)
  • You can configure the balance between the two groups (strength-factor between 1:1 or up to 1:8)
  • works on infrared

Ratio buttons not working

One remark: When first trying the ST-E2 it would only allow me to turn on the ratio once and change the ratio-strength once. The moment I took a picture it would ignore my attempts to balance it - turning it on/off again would allow the change again until the first picture taken. Don't worry, it's not broken; This happens when the camera is set to manual mode! So just set it to another mode (for example Aperture priority) and you can tweak the ratio like expected.

Ratio Tutorial

To test the device I setup a scene with two canon speedlite's ( 430exII and 430Ex) with the subject inbetween.

With the Canon 550D you have a depth-of-field preview (button on the left-hand side, front of the camera). This also triggers a 1 second preview of the light (the speedlite's will flash continuously for 1 second). Note that this makes the flashes run hot, so don't do it more then a few times (or the flash will trigger the 'heat-protection' mechanism and shut itself down for some time).



My (very patient) test-subject with a speedlite flash on each side
The camera (EOS550D or Rebel T2i) has the ST-E2 installed in the shoe. The speedliteon the left (canon 430exII) is set to channel 1, group A
The speedlite on the right (canon 430ex) is set to channel 1, group B


ET-S2 with a ratio of 8:1
Notice the strong left flash compared to the weak right flash - and the shadow on the right part of the wall.
canon st-e2 ratio 8:1 canon st-e2 ratio 8:1 subject canon st-e2 ratio 8:1 result

ET-S2 with a ratio of 1:8
Notice the strong right flash compared to the weak left flash - and the shadow on the left part of the wall
canon st-e2 ratio 1:8 canon st-e2 ratio 1:8 subject canon st-e2 ratio 8:1 result

ET-S2 with a ratio of 1:1
Both flashes firing on the same strength - the shadow on the wall is on both the left and the right side
canon st-e2 ratio 1:1 canon st-e2 ratio 1:8 subject canon st-e2 ratio 8:1 result

ST-E2 conclusion

For testing it's nice to see the 'extreme' situation with a 1:8 balance. In practice it's probably a better choice to go for something between 1:1 and 1:4.

This kind of setup is used for portrait photography. If you use the on-camera flash you will get hard shadows behind your subject. With the remote triggering using the ST-E2, you can let the light come from one side and fill in with a bit of light from the other side. This avoids the hard shadows which can fall on wall behind your subject when using an on-camera flash.
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