How can Dolby Vision and the like provide more saturation and more brightness vs SDR? Why can’t SDR just tell the monitor to go to its maximum brightness or use the saturated colors that it can?

Question

In all “demos” they show a slightly desaturated / dull / dark image as the SDR and the opposite as Dolby Vision (or whatever).

While I understand that DV can provide more resolution (e.g. finer / more grades between shades or colors) I don’t understand what stops SDR to simply ask maximum pure red (as in 255:0:0 in RGB). I understand that the equivalent in DV would be something like 1024:0:0, but if both are mapped to the maximum red a monitor can produce I don’t get how DV can be brighter or more saturated..

In: 17

Answer 1

So it depends on the types of panel. If it’s OLED, then it’s very easy to get that high contrast, because individual pixel is lit independently of each other and it emits light itself.

If we are talking about LED panels (actually just LCD screen over LED backlight), there are 3 types: backlight, edge-lit, full array local dimming. LCD pixels themselves are not able to provide sufficient contrast, they are colored filter which filters the backlight (LED) and display the colors.

To enable higher contrast, the intensity of the backlight need to differ, so the edge-lit have individual LEDs around the edge of the display so they can adjust the brightness depends on the stuff being displayed on the monitor, if that area is block, then it can shut down the LED and make that zone darker, compare to a single backlight which is always lit.

Full Array Local Dimming takes this a step further by having an 2D array of LED behind the LCD, so the localized contrast is even more dramatic, obviously the more zones that it has, the better the local contrast will be.

Dolby Vision is just a certification to say that a particular monitor meet a certain criteria of color/contrast as defined by Dolby Vision parameters. Some companies might choose to not pay for such certification.