Originally posted by npc There's no reason to do that (open to focus...stop down to meter/shoot) on an A7 - EVFs don't not get darker if you stop down (ok, if it is _really_ dark and you stop down, then the EVF's refresh rate might drop to some annoying level)
Ummmm...the issue is not brightness. The issue is focus precision. Stopped down, the image on the focus screen or EVF is bound by the same rules for DOF as the final image and the plane of focus is difficult to determine. The same issue also affects focus confirmation with manual focus lenses. Magnification helps some, but is not a panacea. Back in the day, much of the rational behind owning faster glass was that nailing focus is much easier when you can see what is not in focus. For that the lens needs to be both fairly fast and wide open.
There is a reason why automatic aperture (actuation) was a huge selling point* for SLR lenses in the 60s until the feature became virtually ubiquitous in the mid-70s. Once the aperture was set, you were free to not touch that ring and shoot at will, refocusing as needed between shots, until the light or the subject changed. I shoot an assortment of vintage lenses on both digital and film SLRs and unless I need a particular look, the option for auto aperture wins out every time, even on meterless cameras.
Steve
* That is why it is not uncommon to see lenses from the period prominently labeled as "Auto Somethingar" or similar. On my shelf, I have two Auto Rikenons , an Auto Mamiya/Sekor, and an Auto Focal. Lack of the designation (in name or description) would generally mean a pre-set aperture mechanism or on some specialty lenses, fully manual aperture. Almost all Asahi Optical Company and Pentax lenses since about 1960 have automatic apertures.