color me puzzled about downsampling

[zor]

Why would a downsampled BD from a super higher resolution IMAX source look any better than a BD from a source that is exactly 1080p? (or for that matter in between 1080p and IMAX)?

[Bobby Henderson]

Visit the article at the link below. It's a paper put together by Arri listing the advantages of scanning and acquiring images at greater resolutions and then down-sampling them to normal size for either 2K or 4K output.
Arri "4K+" Paper

Imagery shot in higher resolution formats like IMAX, 5-perf 65mm, VistaVision, etc. will be able to fight off problems like moiré and muddied "frequency sweeps" (like fine stripes on someone's shirt, etc.) far better than something shot pixel for pixel in a format like 1080p. Moiré and other problems don't end up in the finished image.

[aramis109]

Originally Posted by zor

Why would a downsampled BD from a super higher resolution IMAX source look any better than a BD from a source that is exactly 1080p? (or for that matter in between 1080p and IMAX)?

It may not look any better, all things being equal. However, things aren't going to be equal- film used, etc. IMAX cameras have insane capabilities to produce some great masters, and the better quality that you start off with, the better your end product can look.

[4K2K]

With HD video, you can't necessarily capture the same amount of light levels as film so you may end up with clipped highlights etc. Also, with some HD video cameras, it may not be totally uncompressed or 4:4:4 colour etc.

For 35mm verses Imax (65mm), I'd think there should be less visible grain on the finished Blu-ray if shot with IMAX 65mm film and scanned from the original negative than doing the same with 35mm film. They'd be a lot less likely to add DNR if they scanned from the original negative of a 65mm film than 35mm film. Also, with 65mm, as well as having more detail when projected at that resolution is more future proof and will look better when we get higher resolution displays than 1920x1080.

[CirtexHosting]

I have read article under Bobby's link I have to say that it explains and describes fully what you are looking for.

[Neo65]

Because a 1080p scan may not give all the details of 1080.

Adjacent pixels may smear, there's potential digital noise from the ccd/cmos scan element, etc.

Ideally though, the original resolution should be substantially higher than the target one (1920x1080). Going from 2048 to 1920 is not as desirable as going from 4096 to 1920, but it's still better than scanning directly at 1920.

At some point, the scanner itself could be oversampling 2x or more internally and creating the final 1920 wide image, and then it would be able to get better details.