Michellets,
That is an easy question to answer. Less reflective surface the weaker the signal. So the target will appear smaller and deeper. I read somewhere that depth indication is based on a nickel sized object. So smaller targets read deeper than they are and large objects read shallower than they are. I think the method works with all brand if detectors. I used to do this with my Whites IDX Pro to show size and/or depth in pinpoint mode. Used/use it on all my Minelabs to show size. Good video.
Ed D.