Originally posted by tuco I believe the stepless automatic exposure range for the LX extends down to EV -6.5 for ISO 100. So that means you won't be able to meter through the ND filter for low light scenes in the EV3 or EV4 range as middle gray. And I don't know how the meter is going to react when it can't "see" the lower values in the scene if EV3/EV4 is the middle. I guess you'd get a middle gray bumped up a few stops. So to play it safe, I'd consider EV6 or so the lowest light level to meter through that dense of a ND filter.
For sure this is the technical specifications of the light meter. In actual application I have tested the LX to successfully meter over 2 hours and longer as it will continually meter the scene until it has received enough light. Keep in mind that when you do test this, the IDM reads off the film and the pressure plate is not exactly the same reflectivity of film. Of course since this is beyond technical specifications YMMV. However, the results have been consistent in the numerous tests I have conducted but I am not sure if this is consistent across all LX's.
BTW, OM4 will continuously meter OTF but cutoff at 2minutes, Nikons will meter the scene at the time of shutter activation with no cutoff time and will not deviate, Canons - and others, act like Nikons but will cutoff at 30 seconds or less.