yep and some of the 4k titles seem to be a little better to me, 5th element looked better on 4k then bluray to me .maybe some movies done in 4k have a better source ? not sure but they are very clean noise free. and yes resolution is going to be 1080p on the sony 45.what ever you feed it it will only display max res in this case 1080p. i am legend 4k looked only as good as the bluray so i think the newer movies are going to be better (bluray or 4k)
The better the source the better the output.
The higher colour depth and added detail (there is 4x the detail on a 4K disk, that even downscaled will be apparent on the 2k screen) is definitely worth it. It has the added benefit that you can buy 4k discs and then have them ready for when you eventually buy a 4k display.
I think that apart from recent films that are shot in 6k or higher and (crucially) mastered in 4k, then older films actually give a much higher quality HDR transfer than newer films due to them coming from actual film stock/negatives. For example, The Wizard of Oz and Lawrence of Arabia are superb transfers, both in colour and detail.
The original Alien film too..... etc etc
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