I don't post very often (basically never), but I lurk quite a lot. Every now and then I feel the urge to express my opinion. This is one of such occasions.
From the DCI specs on Wikipedia:
DCI 4k Cinemascope cropped: 4096* 1714; 2,3897:1 aspect ratio; 7,020,544 pixels;
Cropping to fit the UltraHD specs: 3840 * 1607 (2.3897:1 aspect ratio); 6,170,400 pixels;
Absolute difference: 7,020,544 - 6,170,400= 850,144 pixels that are LOST; relative difference: 6,170,400/7,020,544 = 0,8789 which implies that MORE THAN 12% (almost 1/8) of the picture is LOST;
DCI 4k Flat cropped: 3996*2160; 1.85:1 aspect ratio; 8,631,360 pixels;
Cropping to fit the UltraHD specs: 3840*2076; 1,85:1 aspect ratio; 7,970,596 pixels:
Absolute difference: 8,631,360 - 7,970,596 = 660,766 pixels; relative difference: 7,970,596/8,631,360 = 0.9234 which means that ALMOST 8% of the picture is LOST.
So it's not about 200 pixels. It's about having ALL the movies that will ever get on blu-ray, or blu ray 4k, or digital download 4k, missing almost one million pixels and about 1/10 average of the original picture (and I'm not considering tv overscan).
It's not about 200 pixels.