slave flash propagation time

Does anybody know how long it takes a typical slave flash (wireless type) to fire up, in response to the main flash on the camera. If not, do you know if it is possible to have a shutter speed that is too fast for the slave to react in time.

Would I be right in believing that for high speed photography, with a shutter speed of say, 1/1000th of a second, the slave flash is still going to be quick enough.

Wireless flash and slave flash are different things.

Wireless refers to flash units that comunicate via infra-red or radio, and these have all the features of on-camera flash.

Slave simply means flashes that are triggered by a flash of light.

There is nothing typical about how long either will recharge. It depends on all sorts of factors.

Every camera has it's specified maximum flash sync speed, and this (for Pentax SLR cameras) falls in a range from 1/60 to 1/250. 1/1000 is out of the question unless you are using the AF360FGZ flash gun, which fires a short burst of separate flashes very rapidly. Not many bodies support this.

Normally, it is the flash that freezes the action, not the shutter speed, because the flash is typically of very short duration. To freeze action using flash, the light from the flash must be much greater than the ambient light. This can be difficult to achieve on a bright day.

The time that I was interested in, is the time between the main flash going off, and the slave flash sensing this and firing up. If you were to photograph a fast moving object, with a slave flash setup, would you get a double image? (one from the main flash, a second from the slave).

Would this delay be measured in nanno seconds, or is it something a bit more tangible. I am looking to capture a subject moving at about 50 Metres per second from a distance of about 6 metres, using 35mm lense.

I have tried it with a single flash and results are OK but I need some fill in lighting. A slave flash would be ideal for this, provided it doesn't have a percieved delay.

There is obviously some delay, but it is very short. The object you describe is doing roughly 110mph. If the slave delay is enough to make a difference (which is possible), then make the slave your more powerful light source, and you will then get a second-curtain-sync effect, which will emphasise the speed that the object is travellng at.