I realized today that autoISO doesn't work as simply in the SL as it did in the Ms. In A mode, when you have too little light to take a picture at the Max ISO and min shutter speed, an M further reduces shutter speed as long as it can provide a meter reading. The SL refuses to further reduce shutter speed (perhaps because it cannot provide a decent image at the taking aperture) and you have to shift to M mode or at least fixed ISO to push it down further. Godfrey had commented on this a while back, but no one related his comments to their practice at that time.
is worth comments or further discussion.Yes, AutoISO behaves this way in the SL: when you're past the range you've set, you'll get underexposure. When you switch to a fixed ISO setting, the exposure times will lengthen to maintain proper exposure ... up to a point. As you close down the aperture more and more with adapted lenses in low light, you'll run into the range limits of the metering system—at which point you'll get underexposure again. You can see this happening when using Manual exposure mode too. There comes a point where you're past the range limits of the metering system (because it's trying to meter with the lens stopped down) and that ultimately results in underexposure if you follow the meter's recommendations.
With the SL's 24-90 lens, this doesn't happen until you're in MUCH lower light because the lens is held wide open at viewing/metering time, normally.
I wrote about this behavior on the LUF a week or two ago. No one commented. The SL seems a bit tighter on range limits with adapted lenses than some other cameras, but I've seen the same behavior with other cameras to which I've adapted my lenses.
BTW: It would be nice to ask questions like this in threads separate from the "Fun with the Leica SL" thread. Nearly all SL questions and opinions have all been going into just this one thread, which I thought was supposed to be about sharing photos made with the SL like other "fun with ..." threads. Can we put pictures here and discussion/questions/etc into other threads that pertain to the specific topic of discussion?