Quote Originally Posted by Chan Tran View Post
The Pentax LX when meter in manual doesn't measure the light off the film but rather via the piggy back mirror that reflects light to the sensor (similar to that of the Nikon F3)
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.