Thank you, Larry. Does the camera understand that the attached lens is not native and that the aperture won't be controlled by the body?
For example shooting a native lens set to f8, the metering would be via wide open lens, and the body would stop it down to 8 when taking a shot. My worry is that if I shoot a non-native lens at f8, body will meter a scene at f8 thinking it's metering wide open, and then attempt to stop the lens down? Or does it know that the attached lens is not native because it will not engage various pins inside the body when mounted?
You may be overthinking this. I was pretty much talking about the Contax bodies with meters, though the basic ideas more or less apply to the fully mechanical bodies like the S2.
The camera doesn’t understand that it’s a non-native lens, but if you are doing stop down metering, which you would have to do with an M42 lens, the camera doesn’t need to understand that. The bodies all use through the lens metering, so the metering is determined solely by how much light is passing through the lens; the meter doesn’t know or care who made the lens, and the pin doesn’t come into play since,
because you are doing stopped down metering, you have already taken the automatic stopping down of the lens, via pin actuation, out of the equation. It would be
perfect if one could use every M42 lens on e.g. and Aria or 139Q body, and, no matter where you had the aperture set on the lens, the blades were always wide open until you released the shutter, and the pin arrangement instantly closed the aperture down to the preselected aperture and the metering system took care of the rest. This is only going to work with lenses which are compatible with the bodies they were designed for. M42 lenses are only going to provide this function for M42 bodies, and even then, there are a lot of M42 lenses which will only provide this level of automation on the bodies they were made for, not just the manufacturer but the model as well, because pin placement which varied from lens to lens creates incompatibility.
When I was trying to use one M42 lens from one manufacturer on an M42 body from another manufacturer, where the only option was stopped down metering, it was often unsatisfactory because the viewfinders were so dim at f8 that, if you wanted to shoot at f/8, you couldn’t possibly compose at f/8, you had to jockey back and forth between metering at f8 then opening it wide open to compose or vice versa. It was a lot of monkey motion, which is why few people were in love with stopped down metering.
My proposition, based on experience with, instead, using any M42 lens you have on metered Contax bodies, is that the viewfinders are bright enough that most of the time you can just set the camera to “auto”, set the aperture on the lens to whatever you want for the scene, and compose and shoot without having to do all the back and forth normally inherent to stop down metering. The camera doesn’t know you have a Takumar or Flektagon mounted, and it doesn’t know that when the shutter is released the body wont be able to automatically stop down the lens. It won’t be stopping down the lens, even though it’s trying; it doesn’t need to because you have already stopped it down. Camera doesn’t know, native or non-native, doesn’t need to know.
So, I am just using these M42/Contax setups as auto aperture metered cameras. Let’s say I have a 35 Flektagon on a Contax 139Q. I set the camera shutter speed dial to “auto” and look at the scene through the viewfinder. As I change the aperture on the lens, moving from wide open to more and more stopped down, the image in the viewfinder becomes progressively less bright and I can watch the meter selected shutter speed change, in the readout, in concert with the aperture selected. The image in the vf rarely gets so dim that I cannot easily compose. When you have the aperture shutter speed combo that you want for the scene, just take the picture.
In really dim situations this does become less easy, but most of the time it’s not an issue.
Hoping this has made things more clear rather than less so. Bottom line, if used like this, the lens doesn’t know it’s not on an M42 camera, and camera thinks it’s just another lens letting light through to its meter, which meters just as usual.
For me, these cameras with adapters, are just nice, easy to use, universally compatible M42 cameras. I treat them like that, leaving adapters permanently on 139 bodies and only using M42 lenses on them. I use an ST and RTSIII for Contax lenses. I have too many cameras, but it’s easy enough, probably simpler/saner to just use one body for everything.
