Howard Lester wrote:
"MangroveRoot" wrote

Would I be right in the belief that this question, and the solutions to
it,
would be applicable to formats other than "large",
should one care to do such a thing?

If the lenses you use for your 645 are attached directly to the body, and
especially if your 645 has a built in TTL meter, the answer is "no." If your
lens attaches via a bellows, and your 645 doesn't have TTL, then the answer
is "yes." The greater the extension of the lens from the body, the greater
the required exposure.

That would be a "no" on both counts.
I *do* have a set of metal extension tubes, but that's not the same thing.
I was just curious. Sometimes it's nice to know more than I think I'll need.

Thank you Howard and otzi; your answers were ... illuminating!