550EX or 540EZ on EOS 3 and EOS 1D MKII
I found a very good price for 540 EZ on eBay, like nearly 1/3 of the 550EX normal price... and want to be the winner of that...
However, 550EX is described as special dedicated for EOS 1(v/n) and EOS 3 and EOS 1D(s) (mkII). 540EZ is described as for all A-TTL. What does A-TTL mean?
One is special dedicated, the another one is not, are they different in practical use? What sort of difference?