I was using someone else's Sony ILCE-6000 with an E 55-210mm F4.5-6.3 OSS lens attached. It had shutter lag in excess of a second. Half-press felt non-existent in that the camera did not appear to respond and I did not feel the typical resistance before a full press. The LCD did not show any change in focus, and I did not hear any auto focus motors. Multiple times, the camera shutter fired while I was lowering the camera to examine it.
The owner of the camera said this lag is normal when using that lens. With the E PZ 16-50mm F3.5-5.6 OSS kit lens was attached to the same body, the camera performed as expected. Half-press worked as expected. Lag was no more than expected from most digital cameras.
The environment was indoors with incandescent spotlights. Exposure with a FujiFilm camera in the same environment and similar lens was 1/40 sec at F5.6 with ISO 5000.
It seems strange that changing lenses would so noticeably affect camera function because I have not noticed anything similar while (briefly) using DSLRs (Canon, Nikon) or two FujiFilm cameras with long lenses, such as XC 50-230mm F4.5-6.7 OIS II. With the FujiFilm cameras, I can hear OIS and autofocus working, as well as see focus changing on the LCD.
I know modern lenses and bodies communicate with each other, but it's not like the lens is saying, "Let's lag really badly to give the user a really bad experience." Rather, the lens or body is saying, "Hold on a second (literally)." If it can be deduced, what is the technical cause of this lag? Is anything technologically useful happening?