Originally Posted by Zoltank
Can anyone explain to me why this is happening
How technical do you want to get? I'm not going to discuss the THX patterns, but I'll compare our comments against DVE. Light in the room and APL of the pattern will affect perception, but to try to keep things simple I'll assume a dim or dark room and a low-APL pattern.
The middle bar on the DVE pluge is reported as 2% above black, which is 20 or 21 for how we label bars. So if you set brightness low enough so that the 2% bar on the main DVE pattern is just barely visible (your 57 setting) then it's likely that the Black Clipping Pattern from our disk will begin flashing nearer to 20 or 21. If on the other hand you set brightness so that 17 just begins flashing on our pattern (63 setting) then the above black bars on the DVE pattern will be brighter.
On many digital displays the actual brightness of black will likely remain the same regardless if the lower (DVE 57) or the higher (AVS 63) setting is chosen. There are basically just two things that are likely to change - clipping and gamma. Clipping is indicated by the AVS Black Clipping Pattern, so using the lower setting you will be losing a bit of information near black for very dark scenes. By clipping higher than black, like the lower DVE setting indicates, then that will raise gamma near black. A higher gamma near black just means that dark shades near black will be darker.
So to sum things up so far, the lowest brightness setting possible with either disc will likely cause the following on many digital displays:
DVE - Some clipping above black with darker shades near black.
AVS - No clipping above black, but shades near black will be brighter than if you lowered brightness and clipped levels above black.
On a few displays it would be possible to account for both clipping and gamma and arrive at about the same brightness setting for either the DVE or AVS patterns. To do this though you will likely need to be able to adjust gamma, because brightness on many displays is mainly just a clipping control. A majority of displays do not have a way to adjust gamma, and for the ones that do it's probably best to use measurements to get an idea of what is going on with gamma.
how I can compensate for it? Even as it is, at a brightness of 57 my blacks are a little too gray for me.
I'm not familiar with your TV, so I can't comment if it might have any other controls that would affect light output near black. Generally if the TV is set as dark as possible and a full field of black is not dark enough for you, then like Michael TLV commented all you can really do is to use more light in the room or buy a different display.