Sigma fp: What's the Point of 12bit DNG RAW? One is True HDR Video

Started 3 months ago | Discussions thread
xpatUSA Forum Pro • Posts: 17,666
Re: Sigma fp: What's the Point of 12bit DNG RAW? One is True HDR Video

Markr041 wrote:

xpatUSA wrote:

Markr041 wrote:

A "true" HDR video is a video with an extended color gamut and more color gradations - more colors - and greater dynamic range compared with standard definition (REC709, 8bit), which characterizes almost all monitors and TV's and video shot by most cameras. 12bit DNG RAW clips have the extended color gamut (REC202), and more color gradations (12bit) ...

It's "Rec. 2020".

But what percentage of people here own output devices that have the Rec. 2020 primary colors of 630 nm for the red, 532 nm for the green, and 467 nm for the blue?

...and the full dynamic range and resolution of the sensor (12.5 stops versus the standard of about 6).

My cheapish NEC sRGB monitor is capable of 1000:1 real contrast, just under a DR of 10EV, my SD9 had a measure DR of 9EV (Bill Claff), so where does "the standard" of 6EV come from? Please explain ...


Are you familiar with "just noticeable color difference"?

Discerning a 1-bit difference in 8-bit sRGB is virtually impossible, so how would anyone appreciate the "more color gradations" in 12-bit that you are promoting above?

This poster, besides correcting a typo - thanks!, questions where the 5-6 stops of Rec. 709 (SDR) video I claim come from, and he also claims that having more than 8bit color is not noticeable, nor is having a very wide color gamut. I guess he is questioning any claim that HDR video is visibly superior to Rec. 709 or SDR video. This is based on ignorance of the theory, ignorance of video standards, and has to also come from never having actually viewed an HDR video in HDR. I know of no one who cannot notice the difference.

Where does the REC. 709 standard come from and is it relevant? Rec. 709 is a true, adhered-to standard. It was set by the ITU-R in 1990 *for all HDTVs*. You can look up what the ITU-R is and where it is headquartered (hint: Geneva). This standard is the default in almost all video cameras. It is the standard for blu-rays. The standard limits the both dynamic range and the colors you can see - and you can see the difference when those limits are exceeded.

The REC. 709 standard specifies that there are 5 stops of dynamic range. It is slightly more than that with superwhites. It does not matter what one's display is capable of, video shot in ITU709 or Rec. 709 has only 5-6 stops of dynamic range. That is a specification. HDR video allows many more stops than that. Almost all the video you see has 5-6 stops of dynamic range even if your camera's sensor has 15 stops of DR or your display can show 12 stops.


As to the number of color bits. Look up "banding." The sky, for example, is not one uniform shade of blue, it has many gradations, but 8bit = 256 shades per pixel, so a very pure blue sky can only have 256 shades in a Rec. 709 video, but in reality it has a lot more. And in 8bit color all those gradations are put into visible bands instead of finely differentiated shades.


It is true that very few displays can show all those Rec. 2020 (ok?) colors (now we are talking about number of different colors, not shades of a single color). But many displays now certainly can show a wider color gamut than that specified by Rec. 709 (DCI P3 is another standard color gamut that is larger than that for Rec. 709 that many displays can provide).

So, with HDR you can actually make use of those extra stops of your camera or your display and you can see more colors (not just more shades but actually more colors, up to the limits of the human eye (which are actually less)).

Note: To be even more thorough: one will not see a difference between an HDR and an SDR version if the actual scene has no more than 5-6 stops of dynamic range. That should be obvious, but I say this just in case someone tries to come up with a video in which you cannot see any difference. The videos I rendered in HDR and chose to post are specifically ones where the actual dynamic range of the scenes is very high.

A lot of words and no specific references as regards Rec. 709.

From the horses mouth, not one mention of "dynamic range":!!PDF-E.pdf

From perhaps the most respected in the field:

"The dynamic range associated with code 1 is close to a million to one, not just 1/255."

It would appear that video lives in a completely different world than that of normal digital imaging, so I'll bow out from this discussion before I get drowned in a sea of verbiage.

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