I played with development photos in a darkroom a long time ago. I don't think one second actually makes much difference.
replyDepends on how powerful of a light you’re using. 1 second on a 7 second exposure is too much. One second on a 20, not.
replyI don't think 1 second on a 7 second B+W exposure is that noticeable.
replyI'd probably put the typical smart switch hardware/software stack at around 0.25 seconds. Maybe you can but I don't think I'd try to rely on anything much faster than that.
replyIf you did, I would go in the custom firmware for the smart switch direction. A lot of them are just an ESP32 inside, and you could probably get to 0.001 seconds that way (but you are switching AC which cycles on the order of 0.02 seconds, so whatever)