CHOSING YOUR STROBES

TTL and SLAVE - what's the difference?

I've been asked a couple of times about what TTL is...so here's your explanation in 60 seconds:

Generally TTL (through the lense) means your camera and strobe are communicating...so if your subject is nearer - the camera tells the strobe, "no need to fire on full power", a short burst will do (and vice versa).

For this your camera should have a hot shoe and your housing shoud have some wires hanging inside allowing you to connect your strobe to the camera so they can communicate...

SLAVE is when you have a censor plastered outside your underwater housing and all the strobe does is fire once it senses the built-in flash firing...so in this case, you will have to personally turn the dial and control how much power you want your strobe to exert.

Read more HERE, I found this to be an easy to understand post (why re-write the whole story when someone's done a great job explaining the finer details).