Quite often a reference is made to the T-depth of a film holder and if it is to the ANSI standard or not. My question (feel like should know this, but have been unable to find a good example) is how does one measure the T-depth of a film holder (my understanding is this where the film plane resides when the holder is inserted into the back so that the focus on the GG is in the same plane as the film - yes/no/close?)

And then there is the ANSI standard - where does one find this information as well?

Sorry for the basic sort of question, but would like a better understanding...and Thanks in advance as always.