Quote Originally Posted by Les Sarile View Post
And both LX & F3 actively meter off the film plane when mirror is locked up. They differ in that the F3 does not use the patterened screen while the LX does. They also differ in autoexposure mode as the F3 determines exposure at the time of shutter trip while the LX will continue to meter the scene in realtime - varying shutter time accordingly, for as long as it takes to get a proper exposure or the battery dies.
The F3 doesn't meter at the film plane once the mirror is up. It holds the reading taken before the mirror is up and thus the shutter speed displayed in the viewfinder is the one it's going to use. It sends out a signal thru the hot shoe proportional to the intensity of the flash it reads off the film plane during exposure. For the F3 OTF is only for flash as almost all film slrs with TTL flash do.