Problems with Nikon and Slave mode

[matty D]

I've just been trying to use my Profoto B1 in slave mode, triggered by the D810's pop up flash, and I seem to be getting very inconsistent exposures.
One will be as metered, then it might be 2 or 3 stops under, then correct again. Very weird and annoying!

I'm shooting at my sync speed (have tried slower speeds as well), and the flash is in manual as is the camera, so I don't understand what's going on.

As an experiment I used my Fuji X100s to trigger the flash and all exposures were perfect, right up to speeds that matched the flash duration.

So I can only assume it's a problem with the Nikon rather than the light. I then used the air remote instead of slave mode, and it's 100% perfect.

Can anyone shed some light on this, am I missing something here?

 

[matty D]

Ok so I have discovered the problem, but I'm still no wiser as to why it was causing the problem....

I had my pop up flash set as commander (left it on that setting as I often use it to control speed lights). Having switched it to manual, the B1's fire perfectly consistently.
Its also worth mentioning that when I had it set as commander by mistake, I used a light meter and the output would vary wildly, and the B1 would give off a buzzing sound!!!
Now the pop up is set to manual the output from the B1 is consistent and no buzzing sound.

Very odd! My best guess is the commander mode sent out several pulses, each of which was giving the signal to the B1 to fire??

 

[simonbarker]

Sounds about right, your on camera flash was triggering the B1 early with pre-flashes so you'd end up with inconsistent exposures.

First I've heard about buzzing from a B1 but as I've never used one I couldn't say if that's normal or not. The only causes of buzzing I'd normally associate with a studio flash would be the modelling light or something caught in the fan but cheap/faulty electronics can buzz when powered (which is probably not a reassuring thing to hear).