How is 2.35:1 stored in Bluray?

[Ghitulescu]

True, I want to add though, that besides SD dvd, there is another "anamorphic" resolution that is within the blu-ray specs.
1440x1080x59.94i or 50i and 1440x1080x24p or 23.976p (of course both with DAR flag set to 16:9) are possible also (not for MPEG2).

DAR remains however 16:9.

SAR is different, because 1440/1080 is not 16:9 but 4:3. The pixels are not quadratic, and the image is stretched back to 1920 during playback.

This mode was made to be compatible with some HDTV camcorders, also used in studios. For consumers, 1440x1080 is HDV.

Again, the greatest confusion one could make is to confuse the DAR with the mathematical ratio between the number of pixels on both sides. Doing this one implicitly assumes that a pixel is so long as it is wide (in other words a PAR of 1:1), which was not the case in the history of television until HDTV and BD arrived.

[von Suppé]

All in short:

SAR x PAR = DAR

[ChiDragon]

A fair bet is that this is done to keep the movie at 1080p. I'm pretty sure, in fact, 1920x1080 is mandatory for the Blu-Ray format (so as to distinguish it, clearly, as 1080p, needing HDCP verification).
No; see above posts referencing one of the other supported resolutions.

In terms of actual released titles, there have been a few 720p BDs.

[ChiDragon]

Any idea why it's done like that?
Behind-the-scenes answer from insider: few elements, no workflow (http://www.avsforum.com/forum/117-2-35-1-constant-image-height-chat/1523706-remember-early-format-d-theater-dvhs-were-2-35-1-films-encoded-more-lines-than-bluray.html#post24515807). He mentions that movies like Lord of the Rings only exist as 2048x858.

[Ghitulescu]

He mentions that movies like Lord of the Rings only exist as 2048x858.

From what I know, Star Wars (the new series, or Prequel) had their special effects "filmed" in 2k (with photocameras, not film cameras), therefore 4k would be then upscaling.