Some pointers with flash photography needed please
I apologize in advance if this has been already discussed.
I have recently started shooting with a flash (Canon 580 EX II) and honestly flash metering has me a bit perplexed.
For one, in ETTL mode, it almost always leads to over-exposure leading me to dial in a -1 to -1 2/3 ev flash compensation for the typical light conditions I've been shootin in.
I am not sure how flash metering works, that it decides to put out so much light that would lead to over-exposure. It has been a trial and error exercise so far with me randomly dialing in a negative flash compensation in the vicinity described above.
Question 1) Why does ETTL behave that way? And how do you folks normally figure out what compensation to use? Is there some rule of thumb I can learn to get this right without trial and error?
Question 2) An extremely strange issue. I put brand new batteries in the flash unit. It fires great. I put a flash extender (BB) and it does not fire, even after many tries. I remove the BB and it fires fine again. Any possible explanation?
The BB lens is not dirty or mucky; and even if it were, I would imagine, if anything the flash would generate even more light after metering through that muck?