I am using windows and paint.net. I want to crop photos while being able to see what it is going to look like. The crop tool in paint.net put a blue shade over the area you are selecting, I want to see the area I am selecting normally with the rest of the photo not visible / shadowed out light box style. I also want to be able to adjust it for maximum effect, make the selection wider / narrower etc. Program must be free. 

Also is it best to crop photos to a standard size or to crop it to whatever looks best even if it is not standard photo sizing?