Measure from film plane or lens?

[Bruin]

I want to test some lenses for focus accuracy at 1m but I need to ask...do I measure from the film plane, front of the lens, or somewhere else?

 

[erikhaugsby]

Measure from the film plane.

 

[spysmart]

Don't know about your ZM, but most cameras (used to) have a datum mark ( for the film plain ).
The standard mark is a circle with a line through and, on the M6, it is under the wind lever.

 

[Bruin]

Great, thanks guys!