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I have been curious about how much information is actually contained on an anamorphic widescreen DVD and I think I have the answer:


- DVD's have a resolution of 720 x 480

- With a letterboxed format of a 2.35:1 DVD, the picture would therefore be 720 x 306 with 174 lines devoted to the black bars on the top and bottom (= 87 lines/bar)

- An anamorphic DVD stretches the picture vertically by 33%. This results in an image 720 x 408 with 72 lines devoted to the black bars (=36 lines/bar)

- Therefore there are 408 lines of horizontal information

- With an 800 x 600 picture in a 2.35:1 format, you can display 340 of the 408 lines (800 x 340), a loss of about 17%

- With a 960 x 540 screen, you can just display all of the 408 (960 x 408) lines of resolution.

- Going above a resolution of 960 x 540 should not buy you any additional sharpness (although you can get other benefits such as less screendoor) because at that point you are merely scaling up the image to a higher resolution.



Can you get a 16:9 anamorphic DVD? If so, then the letterbox version would be 720 x 405. The anamorphic version would be 720 x 540. An 800 x 600 projector could display 450 of the lines and again a 960 x 540 projector could just display all of the 540 lines.
 

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Your math seems about right for USA and Japan DVDs. For UK and Australia, DVDs are 720x576, so you need 1024x576 to not lose anything.
 
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