Im not sure exactly why or how but it's documented often. Understandably watching 1080p content on a 1080p screen will look better than on a 4k screen.
Not entirely true.
The processing and upscaling of some 4k sets makes 1080p videos look amazing. I've just bought a LG55uf860v and running blurays on it gives a much much better picture than on my 1080p tele. Admittedly the 1080p screen is a few years old (2012) but the new sets really do a very good job at upscaling to 4k
It does look stunning.
Amazing TV by the way and fully recommended if after a set for under the £1000 mark. Very similar features and comparable picture quality to the samsung 8500 which is £1600 and is classed as being one of the best screens you can get.
Excluding OLED. Which does annoyingly give an obscene picture that wipes the floor with any other TV. And I say annoyingly as I cant afford one
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