I’m taking a fair number of photographs these days whilst in ‘macro’ mode. One problem I’ve found is that when concentrating on composing the image I’m always in danger of allowing the servoing lens system to collide with whatever I’m photographing. That’s not a problem if it’s a flower but it’s very bad news indeed if the lens makes even kissing contact with some more rigid surface.
So, I propose that the existing autofocus mechanism in digital cameras be enhanced to help avoid ‘parking collisions’ of this type. Basically it requires an af sensor on the tip of the lens and a fast feedback control loop, when in macro mode, that advances the lens by an amount which is always less than the distance from the object (plus some margin for error, based on other significant factors eg my camera shake).