"The preset filter would apply then to the entire image?"
The Computer to RGB preset takes the 0-255 luminance range and drops it down to 16-235.
I generally limit it's use to photos but every once in a while, it comes in handy for video footage.
"Sony could use the shadow/highlight filter from photoshop to make it easier (and that's still little bit tricky to get transition natural unless it's slight correction)."
Glenn Chan has some excellent articles about this and other colour correction issues
on his site.
I encourage you to check them out.
