Ok there's something that I need to clarify 'cause I've been confused about this for a long time.
Does light stack? To illustrate my question, if I were to have a subject lit by strong sunlight from the right and I were to fire a flash straight on(exposing correctly in M mode for the sun-lit side, metering for flash on the unlit side, perhaps dialling in FEC of -2/3 stop), would this result in the light output from the flash adding to the light output from the sun and really blowing the right side of the subject or would I get a nice fill that's 2/3 stops under? So far I've only tried fill flash with backlighting and I cannot predict how it will turn out because I haven't grasped the above concept. Does light work like sound at all?
What is necessary to take note of when shooting with combined lighting?