Hasta La Motion!

Just nor sure on this I have brought a grayscale image into nuke 8 bit and want to render it out as 16 bit, so what I need to know is…….

A) does it change the bit to automaticly eg, as soon as I bring it into nuke its working with 32bit but just not all the information is there to use as a 32bit? if that makes sence

B) I heard of a method of adding a gradient to a B&W image and it gives it a full range? how does this work and how do you correct the colours back to orginal, but keeping the new range?

Thanks People!