[magick-users] Converting 16-bit GRAY files to 8 bits

[Robert Funnell]

I am trying to convert 16-bit GRAY files to 8-bit JPEG or PNG format.
Since the original images are actually 12-bit, I assume that I need to 
right-shift each pixel, so I'm using a command like

convert -size 512x512+3416 -depth 16 -evaluate RightShift 4 -endian LSB gray:c_vf1169.fre c_vf1169_rs4_lsb.png

The effect seems to be that the high-order byte is simply ignored when 
the right-shift is done. Could someone please explain what I'm doing 
wrong? I'm using IM 6.2.4 Q16 as distributed by Debian.

I apologize if this is really obvious, but I haven't been able to 
figure it out or find an answer.

- Robert