I thought I'd start a new thread with this since I want to point Zidoo here after the New Year. Apologies if this ends up like an essay, but I thought it important enough for a full explanation. So there are 3 separate issues with video levels over all the HDR modes: 1. Black and White Clipping - this is where black never reaches black and white never reached white so you get black/white crush. 2. Raised Black Floor - This is where the whole video level is raised so blacks become grey and the image looks washed out. 3. Raised Video background layer - This is where the system generated background layer on which the video is overlaid is raised above black. So, to tackle these one at a time with test results at the end: 1. Black and White Clipping This is the easiest to understand. For 8-bit video (HD BluRay) there are 256 luminance (brightness) levels and for video these are limited to 16-235. For 10-bit video (UHD BluRay) there are 1024 levels, but again for video they are limited to 64-940. (The full ranges are 0-255 and 0-1023 respectively, but as I say, video always uses the limited range) For simplicity and by convention, the Zidoo settings just list these as 0-255 and 16-235 So for 10-bit, black is 64 and white is 940. For HDR it gets more complicated because of the PQ (Perceptual Quantiser) gamma curve and tone mapping, but suffice to say that for a 1000nits signal, white is at approx 723, and this is the signal I used in the tests. So, for 1000nits HDR signal, if black doesn't reach 64 and white doesn't reach 723 then we lose information and the bigger the gap, the more is lost, resulting in "crushed" blacks and "blown" whites. For an SDR signal, white must reach 940 but remember that doesn't mean it's brighter than 723 above - that's all down to the display - these are video signal levels we're talking about, not display brightness. As can be seen in the tables below, the only modes that have correct clipping are Realtek SDR.2020, VS10 HDR and VS10 LLDV. Realtek HDR to be fair is pretty good and because of the way PQ works, you'd never notice in real world content. 2. Raised Black Floor This is where the whole video level is raised with respect to black - so instead of black starting at 64 as it should, it starts at some value above that, say 100, and so black is actually grey and all shades above black have a lighter shade relative to that raised black floor. This means the whole picture looks far too light and washed out similar to this: From the tables below, we can see that Black Floor is raised in VS10 HDR and VS10 SDR. The effect is more pronounced with VS10 SDR since that uses Power Gamma rather than PQ gamma and Power Gamma comes out of black quicker than PQ. 3. Raised Video Background Layer When playback starts, video is overlaid on a background layer which must be set to video black (64). So, for example, if you play a video that has a smaller vertical resolution than the native resolution, the "black bars" will appear black. This is important where 1.85:1, 2.20:1, 2.35:1 or 2.40:1 videos have been cropped which is common practice in encoding. So for example a 3840x1600 or a 1920x800 video must be overlaid on a black background in order that the black bars top and bottom are not visible. As shown in the tables below, this video background layer is not true black for VS10 HDR and VS10 LLDV. This results in grey "Black Bars" top and bottom, and although the video background level is not far above black, it is very noticeable in low light. These graphics are exaggerated to demonstrate what I mean: And you get this when viewing cropped video: As I say, these images exaggerate the effect. 4. Test Results These are the results of testing with Masciola and Mehanik Clip patterns. Mehanik also provides a 3840x1600 cropped black clip pattern (3840x1600) to test the Video Background Layer. The figures in red show what the values should be. As stated previously, these test patterns are 1000nit HDR and these results are with a Zidoo Z9S set to 16-235: As can be seen, the only mode that has correct levels, with no raised black floor or video background is SDR.2020 which is only really useful to owners of certain projectors. As stated in the previous thread by @tosh123 by setting the HDMI Level to 0-255, we can mitigate the raised black floor for VS10 HDR and VS10 SDR but it does not fix either clipping or Video Background. So these are the results for VS10 modes set to 0-255: There is no point showing results for the Realtek engine at 0-255 since that behaves correctly as far as HDMI Level goes. In both cases, VS10 LLDV is usable as long as you use full frame video (or can set masks) In the second case (0-255) VS10 HDR is usable, again as long as you use full frame video (or mask) Although VS10 SDR doesn't look too bad in the second case, black clip is a bit nasty at 76 and white is clipped badly (although this may be to do with the SDR conversion and you'd only lose specular highlights so it's not as bad as it looks on paper) VS10 SDR is certainly a whole lot better than Realtek HDR>SDR since the colour conversion of BT.2020 to Rec.709 in Realtek SDR is terrible.