I don’t often post technical help articles here on the blog, but I took the time to type this to one of my fantastic photographers – and thought maybe just maybe one of you fine folks out there in the interwebbiesphere might enjoy reading it as well…
Aperture automatic is Nikon’s secret weapon that makes its flash system superior to Canon’s (IMHO)!
With TTL the camera takes a meter reading of light reflecting off of the subject to gauge how much light is needed from the flash. When you are shooting a subject that is dressed in all black, that black will soak up a lot of light thus sending back an incorrect reading to the camera. The result: too much light is provided by the flash and the face/skin tones in the frame are over exposed. Similarly, when the subject is dressed in all white (highly reflective), the camera receives back too much light and shuts down the flash prematurely leaving the frame overall underexposed.
With aperture automatic (noted by “A” or “AA” flash mode), the flash puts out a standard amount of light based on the focus (distance to the subject), the ISO, and the aperture – no matter what kind of light reading comes off of the subject. That means it does not matter what the predominant color of the subject happens to be – the flash will be consistent and automatically changed when those three variables are modified on the camera.
Aperture automatic is the step in between manual and TTL – it takes be often incorrect “thinking” out of the camera and eliminates that variance.
When I shoot with gels on my flash, I will