HDR vs. SDR Contrast Ratios

Rory Gordon, Senior Colorist at ArsenalFX Color, during a presentation at a 2019 SMPTE conference entitled “Beyond Better Pixels: How HDR Perceptually and Emotionally Effects [sic] Storytelling”, used data gathered from her work as a colorist on over 35 episodes of HDR content to explore the psychological and emotional impact high dynamic range has on the viewer. In the course of her speech, Ms. Gordon spoke about the differences in contrast ratios between the SDR grade and the HDR trim pass on three shows (and three genres): a one-hour medical drama, a half-hour superhero comedy, and a one-hour spy thriller. It bears noting that, although targeting 1,000 nits for the HDR pass, the mean picture level was actually lower on all three shows compared to the SDR grade. As expected however, the overall contrast of the HDR deliverables increased. The graphics below demonstrate the marked difference in contrast ratios between the SDR and HDR grades, using measurements of the skin tone key and skin tone fill levels.

Upon examination of the contrast of the HDR trim pass, it was found that in some cases, both the key and fill sides increased; at other times, the key side increased while the fill side decreased; and at times (in very dark scenes), both the key and fill sides of the faces decreased – establishing the importance of trimming according to the program’s style, not just hitting nit targets.

3 thoughts on “HDR vs. SDR Contrast Ratios

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  1. HDR what it entails for the viewer brightness wise, I could take it or leave it. But the increase in color fidelity, depth and smoothness is something that should become standard.

    1. Color volume is a combination of hue, saturation and brightness. Greater color volume means better accuracy and more vivid colors. “One of the problems with restricting maximum brightness to 100 nits (with SDR content) is that the brighter the color, the closer it becomes to white (the brightest color) – so bright colors become less and less saturated.

      As an example, the brightest saturated blue on a 100 nit display is only 7 nits, so a blue sky will never be as bright or as saturated as it should be. In contrast, at 600 nit maximum brightness (peak white), blue would be 43 nits; at a peak brightness of 4000 nits, blue would be 289 nits; at a peak brightness of 10,000 nits, blue would be 722 nits.” AVS forums

      1. Wow I never even thought of that. I wish we would get over the threshold for HDR implementation wise. Even now you have to comb through 5 pages of google search results and some really obscure youtube videos to find the bits and pieces to color and edit HDR and the delivery part.

        I had to watch so many videos and forums before anyone even said that first off to get accurate brightness and color you need an add-in card from Blackmagic.

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