Originally posted by butangmucat I currently use a Sony MILC for my K-mount lenses (native K-mount and M42 with aftermarket adapter) with stop-down metering and Av mode for almost all my shootings, and I don't find stop-down a problem...
To each his own, I guess. Automatic aperture actuation (auto-aperture) has nothing to do with metering and was a huge innovation when it first became available.* With an auto-aperture lens in place there is no need to manually stop the lens down to expose after focusing wide open. It is this feature that allows SLRs to be used for any type of photography where focus adjustment is frequent and timing is crucial. When a lens is adapted, this feature is generally lost. I use my M42 lenses on my K-3, but almost never on my K-mount film bodies; they are too cumbersome when I have perfectly functional M42 bodies at hand.
Steve
* In the 1960s into the early 1970s, the feature was called out for marketing purposes. That is why so many M42 lenses are labeled "Auto". Alternatives had manual or preset apertures, both of which types persisted until fairly recently (e.g. former Soviet Jupiter-9 and Helios 44-3).