"Partial zoom" distorts. It does a 100% width expansion, but only about 50% height expansion. "Full zoom" on letterbox shows does a 100% width expansion, and slightly more than 100% height expansion -- the left and right edges fit on screen, but the top and bottom go off the top and bottom. What I want: Full zoom that does not make the top and bottom get lost. A partial zoom that correctly maintains the aspect ratio, losing some of the height on SD shows. ** What I want: "Automatic zoom", that does nothing on wide HD shows (already full widescreen TV size), full zoom on letterbox, and partial zoom on SD size shows. (That should probably be an option -- some people may want letterbox made bigger, and others left alone.) NB: If I'm watching an HD channel in PIP mode, the receiver already adjusts the size/aspect ratio as needed when the picture changes from a wide show to a normal show. Adjusting for letterbox/tall SD doesn't seem to be much harder to me.