We have had several projects now on the Triangle Strobist, yet we have not stopped to really figure out this flash off of our camera. When your camera works in TTL mode, it measures the background light and tries to adjust the flash to illuminate the main subject at a level close to that of the background. This keeps you from having a pitch black background as you used to have with bulb flashes. The great thing about taking your flash off of the camera and setting the exposure manually is that you can determine how well the background is lit and not leave that guessing to your camera.

Here I have shot 7 different images. I adjusted the camera in manual mode for the flash I had so that I would get proper exposure of the main subject (who is that ugly guy).

All shots were at F/11. The exposure times changed in this order (1/200, 1/125, 1/60, 1/30, 1/13, 1/8, ¼) Note how the flash takes care of the exposure of the subject. The exposure length takes care of how well the background is illuminated. I reached a neutral point around 1/13 of a second, the flash began to equal the background light. After that the subject was illuminated by both the flash and the ambient and was thus blown out. So TTL is good, but it is like an automatic car. It serves your interest most of the time, but occasionally you need to control what the RPM’s are. That is when you take the flash off and shoot in manual mode.