How much of Blu-ray resolution do we actually use?

[HDMe]

They would have to amend the spec to allow for other things... and player firmwares would probably have to be updated as well.

The HD spec calls for all HD broadcasts and Blu-ray to have a 1920x1080 image... for the 2.35:1 movies, they fill 200 lines or so vertically with blank space... for 4:3 movies you get blank space on the sides... but it is always a 1920x1080 image being transmitted.

This is different than the way DVDs were... since the anamorphic DVDs allowed for self-adjusting to 4:3 or 16x9 TVs.

Someone could do this for HD and Blu-rays... but I guess they just didn't think about people with projectors.

I agree, though, it would be cool if people with projectors could have full 1080 lines and then the equivalent additional horizontal resolution... but then that would mean more data on the disc... and either more compression to fit it or something since it would take more space than the current way they do it.