Control pt. fine tuning?

Is there a way to fine tune the slider motion in a control point?

I have a control point. I want to get contrast to exactly the right value, down to adjusting a single digit. That is, I went to go from 53 to 48 without a lot of twitching the slider back and forth until I finally hit want I want. (See the “why” below)

At this point, the only option for fine tuning is to enter a value directly. Using the situation above, double click the 53 in control window, type in 48, , done. If, for example, I held down and then moved the slider, the values would change slower than just moving the slider. Does this exist?

Why? Often I find there’s a tipping point between too much and not enough. Most frequently it’s adjusting the radius of the circle around the control point. For example, I want to enhance the glint in someone’s eyes. If the circle’s too big, the face might be altered, too.

In some cases, just the right value (brightness, structure, etc.) matters. Move too far one way or the other and either the effect is too obvious, or not present at all. My current work-around is a binary search (real name). Pick a value that’s close but “not enough”. Jump to a value that’s “too much”. Try halfway between the two values. If the result is “too much”, pick a value between 10 and 15. If it’s right, all done. If it’s still not quite right, try 12. Is that right? Wash, rinse, repeat.

Sure would be nice to have a “vernier mode”, if it exists. Does it?