Originally posted by MJKoski Yes. Only aperture which worked good with Leitaxed Zeiss 28/2 was wide open. And that was when shutter speeds were "fast" under 1 second. Even wide open started to fail when light levels dropped ~10 seconds being some kind of limit. However in Av mode histogram updates as aperture is selected and it works in good light.
It appears that yours is a special case with very low light levels perhaps with that lens and perhaps with the K-1. Since I don't have that camera, I should probably stop typing. But, since my previous results were based on actual tests with my K-3 and other users have reported satisfaction with other models, I will continue.
I had previously compared Av and M in live view with manual aperture, but did the test series under conditions where ambient light was strong enough to allow a full range of apertures to f/22 without going below 1s shutter speed. Just now, I found a dimly-lit closet where the light was measured (Gossen Luna Lux) at EV 3.* An exposure for that EV (f/2 @ 1/2s) of a blank white wall resulted in a centered and symmetrical histogram. I recorded metered shutter settings for the range f/2 - f/16 in both Av and M modes using my Helios 44M with aperture in M mode. Av and M agreed at all apertures, but both were only linear** to f/11 (EV -2 at the sensor). Based on that, I consider EV -2 as the practical low light sensitivity limit for live view metering.
As mentioned before, I don't have access to a K-1 and would welcome some findings for stop-down metering using a controlled process with that camera.
Steve
* I hate using "EV" in this way since the term originally referred to a combination of shutter speed and aperture (quite literally "exposure") independent of film/sensor sensitivity. The values above are for metered EV at ISO 100.
** By linear, I mean a doubling of metered exposure time for each full stop as the aperture is narrowed.
Last edited by stevebrot; 07-12-2018 at 11:10 AM.