Experiment didn't go as expected: Off camera flash question

[Pegasus_Thrust]

Here's a chance for all you old pros to take the mick out of a comparative newb.....

Just tried to do a bit of off camera flash in a darkened room, consisting of 2 manual speedlights on 1/1 behind a brolly on a stand set in slave mode with the flash being triggered by my on camera flash set on reduced power pointed behind.

Expected: A dark subject lit to some degree from an angle with the light provided by the speedlights
Got: A dark exposure as if the speedlights didn't fire (indeed turned off the off camera speedlights and took it again and it was the same)

Setting wise, the camera was set to it's lowest ISO, shutter at 1/125, f9 (all obviously to under expose so were reliant on the speedlights to provide the light)

I messed about with it, trying various positions/settings etc. but it wasn't until I changed my ON-camera flash into manual (from TTL) at lowest power did it work.

Now in hindsight having it in TTL was daft and I was essentially being lazy (so please don't get on the high horses over this) but what I can't get my head around is as to why technically it didn't work??? in my mind I essentially significantly reduced power from the on-camera flash in the same was as reducing the power manually (in my eyes)....... but I just can't work out as to why the camera seemingly managed to take the picture like the 2 off camera flashes weren't even in the room (they definitely were incidentally and they definitely fired and illuminated the wall)


If anyone would like to shed some light on this (BOOM!) I'd be most appreciative

 

[Phil V]

Here's a chance for all you old pros to take the mick out of a comparative newb.....

Just tried to do a bit of off camera flash in a darkened room, consisting of 2 manual speedlights on 1/1 behind a brolly on a stand set in slave mode with the flash being triggered by my on camera flash set on reduced power pointed behind.

Expected: A dark subject lit to some degree from an angle with the light provided by the speedlights
Got: A dark exposure as if the speedlights didn't fire (indeed turned off the off camera speedlights and took it again and it was the same)

Setting wise, the camera was set to it's lowest ISO, shutter at 1/125, f9 (all obviously to under expose so were reliant on the speedlights to provide the light)

I messed about with it, trying various positions/settings etc. but it wasn't until I changed my ON-camera flash into manual (from TTL) at lowest power did it work.

Now in hindsight having it in TTL was daft and I was essentially being lazy (so please don't get on the high horses over this) but what I can't get my head around is as to why technically it didn't work??? in my mind I essentially significantly reduced power from the on-camera flash in the same was as reducing the power manually (in my eyes)....... but I just can't work out as to why the camera seemingly managed to take the picture like the 2 off camera flashes weren't even in the room (they definitely were incidentally and they definitely fired and illuminated the wall)


If anyone would like to shed some light on this (BOOM!) I'd be most appreciative

Your TTL pre flash was firing the off camera flashes (before your shutter curtains opened).
It's not a mystery.
Get triggers, they're not expensive and they remove all the guesswork and half the things that can go wrong.

 

[Pegasus_Thrust]

Ahhhhh!!! Cheers Phil- of course. I have triggers incidentally, but it was 'meant' to be just a v quick test.