I've had my Nikon D90 for nearly two years now, and I wanted to try and experiment with flash a little more.
Reading up on the Nikon TTL system I just can't understand how the on camera flash which needs to trigger the off camera flash would interact with the photo.
I've watched videos of people demonstrating the system, but not discussing the effect of this extra light source. I'm guessing that the off camera flash somehow makes the on camera flash redundant?
If you had triggers (like Pocket Wizards) , it wouldn't be a concern - but what are considerations with the TTL system?