Why does my canon 270ex ii not act as slave?

Question

I have it set to slave and mounted it on its stand.
Im shooting in a small room.
When my camera flash on my canon 40d fires, the speedlite does nothing.
I can't see any setting on the camera that would it as master.

Anyone help?

Answer 1

That isn't how it works. To use it as a slave you need a flashgun on the camera that has the master electronics along with infra-red transmitter and receiver. Communication is via infra red not triggered by a light flash. You need a 550EX, 580EX or 600EX to act as master to the 270EX slave. Alternatively you can use the ST-E2 flash trigger or get a EOS600D or 650D that have in-built triggers.



You can't use you 40D with a flash-light triggered slave because the camera emits a "test" beam to determine exposure an instant before the main flash. This test beam triggers the light sensitive slave which is used to determine exposure, your light triggered slave then doesn't have time to rechcarge before the main flash fires, causing under exposore.

Answer 2

In a small room, light bouncing off walls should be enough to trigger it. Do make sure though that the sensor window is facing either the flash or the subject that the light will be reflected off.



Daft thing, but be such which one IS the sensor window. The slave sensor on some flashes (SOme Nikon speedlights) is actually a small window near the battery compartment, NOT the larger reddish panel on the front of the speedlight (where you'd expect it to be!!)



Tbh I gave up with optically based trigger systems ages ago - they're too unreliable. For £20 you can get a set of radio triggers (RF602's) - far more reliable & much greater range.



Edit: Ah - I keep forgetting, Canon speedlights don't have an optical slave mode - I thought we were talking just optical slave triggering not Canon's wireless system.



Incidentally, regarding BriaR's last paragraph, you can use your pop-up flash as an optical trigger with OTHER flashes that have optical slave mode. The 'pre-flashes' BriaR refers to are only if the flash is in TTL mode. If you can set the flash to manual, you get no pre-flashes & the flash will trigger correctly.



OR if you get a flash like the Yongnuo YN560 (around £50), it has an optical slave mode (S2 from memory) that ignores TTL pre-flashes, so even if you use a TTL trigger flash, it will ignore the pre-flashes & fire on the main flash.

Answer 3

It doesn't work that way. The 270EX II will only be commanded by a 550EX, 580EX, 580EX II, 600EX-RT, or Metz 58AF1/AF2, or cameras 600D, 650D, 60D, 7D.