Hi Les. Although I am not familiar with the LX as I don't have one and not very familiar with the OM-2 as I rarely ever used it. I know the F3 very well and I am sure for ambient light exposure the camera hold the reading from the SPC before it raises the mirror up. For flash exposure it reads off the film plane but it only sending out whatever the value it gets from the SPC to the flash.
Originally Posted by Les Sarile