You won’t see HDR unless very specific conditions are met. Because there’s been a lot of confusion in the past about “HDR” and it’s connotations with those aweful photographic techniques to make pictures look ridiculous, it needs to be established that HDR is more applicable to the consideration of High Dynamic Range image processing. Pivoting on the Linear colour pipeline where colour is physically reliable in it’s behaviour and will operate in a larger range than what the destination display can render there needs to be a tonemapping operation to bring those values into the colour space and range of the display. The UE4 4.15 update brings ACES Tone Mapping which, if I understand correctly, will tone map into a larger range (up to 1000 nits peak or 2000 depending on HDR support) if the conditions are met. Otherwise you’ll get a more familiar image to what we’re used to where the brightest value can only be 1,1,1 = White. HDR on the other hand can have very bright Reds, Greens and Blues ; think Neon or bright blue skies.
The LG OLED E6 will accept up to 1000 nit HDR (I think it can only display up to 800 in the 2016 year model) but the flagship Sony will accept the 2000 nits level.
A lot of 4k TVs accept HDR - and yes, a firmware update can unlock this. But depending on display technology and in the case of LCD, the method of backlighting the pixels, you may or may not get a great HDR experience. 4K is a requirement of HDR too, because the spec supports the wider colour gamuts, frame rates/bandwidth and meta data to enable HDR. It’ll be interesting to see if you can render at HD and pack it as 4k so it’s adaptable to different hardware.
Exciting stuff.
Matt Hermans