after entering the lens length the focus stays in the value box with no way to release other than to click into the viewport. since my viewport is usually pretty full i would like to avoid that. i would say usually the focus should release after pressing enter, or at least with esc since keeping the focus there can be also useful at times.
this is an old bug which i have never gotten around to write up but is very annoying because i dont always (barely at all) think about it, then you just keep typing and have the lens length full of commands wondering why they dont apply and resulting in having to reenter the lens length additionally.