Quote Originally Posted by ic-racer View Post
18% gray (or 12.5%) are NOT related to "middle" gray of a silver print. (The 18% gray card is an exposure tool, not a printing tool).
I'm not understanding this statement.

As I understand it, one of the best reasons for using a reference card is to be able to "place" a subject in relation to a standard.

In the case of a Kodak gray card, if we have a reference shot including the gray card, that "18%" gray shade becomes directly translatable from scene to paper for all the related shots.

If the Kodak card can be considered a "middle grey" subject when it's in the scene, then there is a connection to the print.