I'm wondering if this misnomer adds to the confusion many people seem to have with this simple concept.
If I have a 4:3 screen (and PJ), then my set up is 100% constant width. Every aspect ratio is the EXACT same width. This is true on a 16:9 screen if I never watch 4:3 or 1.66:1 content. But even then, with a 16:9 screen, your set up is constant width for all ARs greater than 16:9 and not-constant width for ARs less than that.
OK. The vast majority of constant height set ups are no where near that. There is much more variability of height than there is width in a CW set up. 16:9 content and 1.85 content are different heights on most "constant height" set ups. 2.35:1 and 2.76:1 content are different heights on a "constant height" set up. 2.2:1 content will either lose some content at the top and bottom, or be yet another height!
What most "constant" height set ups are are really "dual width" setups. You are basically fixed width at either 16:9 or 2.37:1.
The only people approaching constant height would be those that leave the lens in place all the time and scale to not use all the pixels (and do things like slight vertical and horizontal stretching of 1.85:1 so that it is actually wider than 1.78--but this type of set up is not possible with a movable lens). But, even they don't have constant height with 2.76:1 content.
So, why do we use the misnomer "constant height" when to this day, I've never actually seen a true constant height system in a home? "Dual Width" seems to be a much more accurate description of what most people have.
If I have a 4:3 screen (and PJ), then my set up is 100% constant width. Every aspect ratio is the EXACT same width. This is true on a 16:9 screen if I never watch 4:3 or 1.66:1 content. But even then, with a 16:9 screen, your set up is constant width for all ARs greater than 16:9 and not-constant width for ARs less than that.
OK. The vast majority of constant height set ups are no where near that. There is much more variability of height than there is width in a CW set up. 16:9 content and 1.85 content are different heights on most "constant height" set ups. 2.35:1 and 2.76:1 content are different heights on a "constant height" set up. 2.2:1 content will either lose some content at the top and bottom, or be yet another height!
What most "constant" height set ups are are really "dual width" setups. You are basically fixed width at either 16:9 or 2.37:1.
The only people approaching constant height would be those that leave the lens in place all the time and scale to not use all the pixels (and do things like slight vertical and horizontal stretching of 1.85:1 so that it is actually wider than 1.78--but this type of set up is not possible with a movable lens). But, even they don't have constant height with 2.76:1 content.
So, why do we use the misnomer "constant height" when to this day, I've never actually seen a true constant height system in a home? "Dual Width" seems to be a much more accurate description of what most people have.