Better to upscale or downscale for nonstandard resolutions?

[jakhloz]

Hi,

sometimes when I turn source files into DCPs for the cinema I work for, I get a source that sits in the middle between 2K and 4K resolution. Like right now, I've got a file with 2944x1106 resolution (short film in 2.66:1 aspect ratio) and now have to choose to make either 4K DCP and upscale or 2K DCP and lose resolution. I personally feel leery about upscaling, so in the past I've chosen 2K, but I thought to ask if there is some best practice or a recommendation based on how scaling in DoM actually works.

Thank in advance.

[Carsten]

I wouldn't see a reason to prefer downscaling to upscaling. I think no one so far has performed a solid analysis of DCP-o-matic's scaling algorithm. Carl may comment on the actual method being used.

Would be interesting to compare upscaling of e.g. Davinci to DOMs own scaling.

That said, I never saw or heard about a weakness in DCP-o-matic's scaling. We use a 4k high contrast DCI projector that upscales 2k DCPs to 4k in realtime, and I never saw issues. We get a lot more 4k DCPs in recent years, by the way.


Also, the number of 4k projectors in the field is increasing. And especially wide screen formats beyond 2:1 definitely need the higher resolution because they discard so many pixels above and below the active pixel area.