Ah, a golden dog. A warm sunny day. Playing in the water. I miss those around here.
I've been using CIF (AKA trap-focus) a LOT recently. I've stuck metal tape on a number of lenses to use with infinity-focus adapters. But for closer work, and for screwmount lenses (like M39s) whose bases are too narrow to hold metal tape against the camera's contacts, I use a flanged adapter, which shorts all contacts.
With a flanged adapter, we lose infinity focus. Depending on the lens, far focus drops a little or a lot. With one 35mm at f/2.8 it drops to maybe 1.5m, at f/16 to maybe 2.5m. (That 1mm flange makes a BIG difference there!) With one 200mm at f/4, far focus is about 15m; at f/8 it's about 40-45m. (I just paced it off). So that flanged adapter is for situations where infinity doesn't matter. And of course it pulls in the near focus a little -- on the 200mm at f/4, by about 0.1m.
Some of those older, narrow-base lenses would be rather difficult to use well without CIF/trap-focus. And in any case, the camera reacts faster than I do when I achieve focus. Too often with manual non-CIF shooting, I'll reach focus, then the subject or I move before I can press the shutter. Bummer. With CIF, I find myself sticking with wider apertures on longer lenses. I don't need the DOF safety margin as much. Conversely, I'll stop-down softer lenses that I'd otherwise leave open so I could see better. Yeah, CIF is the poor guy's AF for manuals.