Ambient Light: Impact On Dynamic Range

It’s been a while since the bad old days when we used to binge-watch Netflix shows till the early morning hours, first on an LG C7, then on an LG CX, but we began re-watching the gritty French crime series Ganglands last night in order to see whether we couldn’t formulate a more coherent argument as to why bright windows and practicals, far from being a nuisance, are in fact essential to the HDR viewing experience. We also wanted to learn whether the highlights in Ganglands were more or less impactful when viewed on a display whose picture area is 10X greater than our MacBook. We’d just finished browsing fragments of the hugely disappointing season 2 of the black comedy The End of the F***ing World, whose HDR grade was virtually identical to the SDR grade of season 1, much to the satisfaction of the director, the DP and the colorist. This was anything but an isolated incident – many, if not most, of Netflix’s HDR offerings are no more than rubbish SDR wrapped up in a Dolby Vision package and it’s no secret that 99% of shows have zero HDR intent to begin with. As of March 2023, Sky UK is the only VoD provider that requires scripted content be shot with a camera capable of no fewer than 14 stops of dynamic range (essentially ruling out all but ARRI cameras) and that demands that HDR grades offer a perceptual increase in dynamic range over SDR (while at the same time stipulating that grades must look stylistically similar across the SDR and HDR formats!). 

There’s no denying that movies look a heck of a lot more cinematic on a TV as opposed to viewing on a tiny 16” laptop, but we were rudely reminded of why the experience was always less than satisfactory: the entire room lights up like a Christmas tree when watching content on a 55” display, degrading image contrast and destroying the sense of immersiveness. ‘Perfect blacks’ are the selling point of OLED televisions, somewhere in the neighborhood of 2/3 of the dynamic range of OLEDs is situated below middle gray, yet ambient light just annihilates that advantage. It’s well known that the viewing environment plays a larger role in the ability to display HDR than the range of display capabilities. The actual black level is the sum of light contribution from the display’s native black and screen reflections. The screen grabs, from a presentation by Timothy Lottes (AMD) at a Game Developers Conference back in 2016, convincingly illustrate the relationship between ambient light and display contrast. Decreasing screen reflectance by fifty percent doubles the effective contrast ratio in ambient light. The figures are for an OLED TV with a peak luminance of 400 nits and are only intended to give an idea of general ranges, not specific values. Current OLED TVs have a screen reflectance of around 1-2%.

Which describes your own viewing environment?

Photo: Timothy Lottes
Photo: Timothy Lottes
Photo: Timothy Lottes

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