HDR - It's all down to the nits....

[Simon Dunne]

I've been wondering and searching for a while, to find a true and accurate definition of HDR. Obviously it stands for high dynamic range, but what does that actually mean? We all know the best cameras on the market can offer about 16 stops of dynamic range. Are people able to pull more range out in the grade? Is it talking about colour space? A better display? It's all down to the nits it seems;

HDR – High-dynamic-range imaging (HDRI or HDR) is a set of techniques used in imaging to reproduce a greater range of luminosity than standard digital imaging. The aim is to present the human eye with a similar range of luminance as that which, through the visual system, is more lifelike. HDR enables content creation and distribution of images with higher luminance dynamic range and wider color gamut. For example, while typical TVs today have a peak brightness of approximately 100 nits, the peak brightness of an HDR television is around 1,000 nits.

Today, i came across a newly published UHD guidebook from Dolby, Harmonic and TDG. It's very informative and has filled some gaps for me in my knowledge. Definitely one for Graeme to cast his expert eye over to make sure it's accurate!

Dolby are making great strides into the visual side of the market. It's smart that they've hooked up with Harmonic to cover the broadcast side too. Others involved seem to be Avid (DNxHD) and Panasonic (AVC-Ultra) with their codec offerings (thank god there's no ProRes! :001_tt1

It seems to me that any production shooting 4K now (House of Cards as an example) aren't too far off a UHD deliverable. Just film at 100/120fps, grade in Rec.2020 and encode and deliver appropriately. This is where the .RED encoder might start to show it's true colours. It'll be interesting to see how far RED let their codec develop.

Anyway, the above HDR definition was taken from this new UHD guidebook, take a look, it's a quick data mine with the link in your email

http://info.harmonicinc.com/Ebook-UHD-Guidebook

 

[Graeme Nattress]

High Dynamic Range has different meanings dependent upon context. To a stills photographer it might mean bracketed image shooting coupled with tone mapping post processing. To a camera manufacturer like RED it means capturing a high dynamic range at the sensor and preserving that in the recording and workflow. For a display it could mean something similar, but with displays we get the extra confusion of brightness into the mix. Let me explain:

Dynamic range is usually measured as the ratio of the brightest to darkest the device can record / reproduce. In that respect my Flanders OLED monitor has a very high DR because at it's blackest, the OLED technology produces very very black blacks. If I turn the room lights off, black is so black it's hard to measure how black it is and thus you get a ratio of peak brightness / zero which is theoretically infinite DR, but practically speaking it's still quite a high DR. But it's not an HDR display! For an HDR display you need a combination of good dynamic range from this traditional ratio definition of DR, but with added peak brightness to accurately display highlights without having to use tone curves or whatever to bend them in or roll them off. Yes, you need dark blacks too the "peg" the image and give good contrast, so peak brightness alone won't do it. And that peak brightness isn't necessarily for making a super-bright image either, but to reduce / avoid the need for compressing highlights. This is much more like how we look at dynamic range in audio where that rendition of the 1812 might be loud but not deafening until the canons come in and blow you off your seat. A great recording that uses minimal audio compression (in the audio sense of compressing dynamic range - I'm not thinking MP3 meaning of compression here) and where the amps and speakers can cope with high volume levels without themselves compressing or distorting will result in a very dynamic portrayal of the music.

Graeme

 

[Stacey Spears]

Dolby is focusing on playback HDR. We have long captured content that has more dynamic range than we can view on our 100 nits system today. SMPTE-2084 is the EOTF that replaces gamma for HDR. Though the ITU is trying to produce its own EOTF. You may also hear 2084 called the PQ curve or simply PQ. PQ is more efficient with code values than a traditional gamma curve. The code values also directly map to nits. PQ maps 235 (940) to 10,000 nits. I wish they would have went full range as we are wasting code values above 235/940. In fact, 254 (1020) is around 24,000 nits.

There are competing HDR standards. Blu-ray UHD is supporting HDR10 from both Dolby and Philips. HDR12, which is full HDR is optional on Blu-ray. Vudu announced Dolby Vision streaming at NAB and it was demo'ed on a Vizio R65 display. Arri was showing HDR on a Samsung display in their booth at NAB. It was simply the PQ curve and content graded for it. Sony also had an HDR demo, not sure if it was using the PQ curve or not.

Personally I think HDR is the single biggest visual quality improvement since we went from 480i to 1080p. Its a shame we may end up with an HDR format war.

 

[Simon Dunne]

Thanks for the explanation Graeme.

Its a shame we may end up with an HDR format war.

The BDA have plumped for Rec.2020....

http://www.businesswire.com/news/ho...tion-Completes-Ultra-HD-Blu-ray™#.VVmFuvmeDGc

 

[Gavin Greenwalt]

I refuse to accept any definition except for the correct definition which is to say a wide dynamic range image either in capture or display. So 14+ stops of dynamic range on capture and 14+ stops of dynamic range on playback. (I'm happy to accept other definitions of how many stops is "high" though).

 

[Stacey Spears]

The BDA have plumped for Rec.2020....

BT.2020 defines the gamut, which is wide, and 3x3 matrix to convert from and to RGB, it has nothing to do with HDR. BD supports Dolby Vision and Philips for HDR. Both Dolby and Philips support BT.2020, P3 and 709 in terms of color gamut.

 

[Antony Newman]

Skimming the Dolby White paper : http://www.dolby.com/us/en/technologies/dolby-vision/dolby-vision-white-paper.pdf it occurred to me that I have not seen a graphic representation that shows the eyes ability to see a colour gamut vs light intensity.

Is there a brightness when we see the widest colour gamut?

For sounds - there are huge 'volumes that investigate this for audio - and demonstrate (in amongst other random facts) that we can experience pleasure when exposed to high level low frequency content (which may be why churches have organs!).

Is there an equivalent analysis for light? Do we 'feel more' when exposed to images with 10,000 nit pics vs 100 nits (but with the same dynamic range)?

AJ

 

[Hrvoje Simic]

Wonder if anyone has actually done some tests of the effects of long term exposure to a large wall with high DR stimuli, punching the visual cortex at today's pace of compensation for the lack of substance.

Also, romantic sunsets, sun glare behind faces and bright exterior outside the window change the effect in storytelling with high DR presentation, and blinding the viewer is not the purpose.

 

[Hrvoje Simic]

DOLBY VISION: ROOTED IN THE SCIENCE OF THE HUMAN VISUAL SYSTEM

This sounds so warm and welcoming, thus attracting me to explore this technology further.

There are three ways to improve picture quality for movies, TV shows, games, and user-generated content:
• More pixels: 4K, 8K, and beyond
• Higher frame rate (HFR)
• Better pixels (more dynamic range and wider color gamut):

This sounds great. Even better than great picture quality is the ultra bestest awesomeness.
Hopefully some company can give all of this so every new movie uses just the bestest so I am constantly looking at the most colorful and contrasty movies with most detail possible. Because one really needs to see weaving of the fabric and texture of eye lashes to understand the storyline and feel the emotions.

Dolby Vision 4K televisions have “more pixels,” and newer standards for UHD TV also include high frame rates, but these standards don’t make each pixel better able to represent the full range of brightness we see in reality. Dolby Vision is the Dolby Laboratories solution to meet this challenge. The natural world has a much broader range of color and brightness than most current broadcast,

The difference being:

1) In natural world people turn heads willingly and consciously choose sensory stimuli, they are not fed with it.

2) In a natural world there are no huge robots attacking humans (yet) and there are no edit cuts.

TV display is an additive color system—red, green, blue—meaning that the brightest pixel is white. The problem with restricting maximum brightness to 100 nits (as in TV and Blu-ray) is that the brighter the color, the closer it becomes to white, so the color quickly becomes less saturated. For instance, the brightest blue on a restricted-brightness display is a mere 7 nits, so a blue sky will never be as bright as it should be.

Oh no!


"This great looking blue on my 10 bit quantum led or OLED UHD screen is not exactly the same as outside my window! I'll have to go outside eventually! Crap! Honey, we are going on a beach on Sunday, call the pharmacy and reserve sun, air, water, allergy and bacterial protection pills. And buy batteries for the TV we are bringing".

The last part "as it should be" is the cutest.
Dolby decides what "it should be" for millions. Entitled much ?

HOW MUCH DYNAMIC RANGE DO WE NEED? The Dolby image research team ran a set of experiments with ordinary viewers to answer this question. The researchers tested what viewers preferred for black level, diffuse white level, and highlight level. They determined that a system that could reproduce a range of 0 to 10,000 nits satisfied 90 percent of viewers asked to pick an ideal range.

Looks like a fool-proof test.

Well, good thing they are not making candy for kids.

Though eye-candy premise has similarities.

Dolby Vision gives the director and colorist (or the game programmer and the lighting and effects designer) the tools they need to accurately represent the vibrant colors, bright highlights, and detailed shadows that help draw the viewer into the scene.

"Dolby vision gives the tools necessary to create, enhance and perpetuate a zombified hypnotic state of make-belief, making fantasy replace reality, while the window to reality offers less appealing imagery."

Content creators can now color-grade their content using prototype Dolby Vision reference monitors, which have dramatically higher dynamic range and wider color gamut, to ensure the highest-fidelity mastering.

Because every colorist's dream is treating his eyes with 4000/10000 nits while precisely tuning tonalities for hours.

The Dolby Vision picture contains metadata about the system used to create the final version of the content. Because any Dolby Vision television has been carefully calibrated by the manufacturer and Dolby technicians, our technology can produce the best and most accurate possible representation of what the creator intended.

Because the content creator really intended to show how bright that sun was.

 

[Stacey Spears]

http://www.harmonicinc.com/sites/default/files/Harmonic_Complete_UHD_Guidebook.pdf

 

[Wayne Morellini]

If it has not been mentioned before, peak brightness is a problem. Don't get me wrong in the following, I like bright screens (mainly for certain games), not too bright, but high brightness are practically useless most of the time. There were some TV's over a decade ago that had high brightness (maybe even 1000nits, but looking at a scene with white sand at the beach your eyeballs would ache. Major releases often hardly ever use it. Mission Impossible 2K for instance, tried to portray the bright light levels around Sydney, but it was just stressful. Occassionaly somebody will use it as a special effect in a bright desert scene of a bewildered maybe thirsty lost person, but a lot of audiences will not find it a relaxing view as they lack the high adrenaline and dopamine of film makers. What you get with high HDR and high framerste displays with special effects, likely a lot of law suites about epileptic fits (as they widen the possibility to trigger one). Anyway in a darkened room with eyeballs relaxed and pupils wide opened shining a bright light into some bodies eyes (such as a stage key light on a scene of people on a stage) can be a painful.experience. so the ordinary film maker and TV field production will have to be more careful (like all of us) and I will try to keep the maximum brightness of my future TV to 500 or less nits (300 or so is considered bright enough on computer mointir use).

 

[Wayne Morellini]

Hrvoje, yeah I forgot to mention colorists. They with likely turn down bright scenes to do most of the grading. I wonder how it will go with law suites for cartriac? damage law suites. They will have to have displays specially filtered to reduce ultraviolet and infrared transmission. So much for using the display as a heater on a winters night.

 

[Antony Newman]

Hilarous response to their paper Hrvorje.

AJ

This sounds so warm and welcoming, thus attracting me to explore this technology further.
<snip>

 

[Gavin Greenwalt]

The world is often very bright and we don't see people complaining about it.

 

[John Bellari]

Time to update the dictionary...

NITWIT (redefined 2015):

Standards Committee Members who approved HDR brightness levels subjected to 8hr daily Youtube HDR content, for one year, whom formerly had vision...


There is an analog in the Audio Industry- see "Loudness Wars", now we gets ours:
"BRIGHTNESS WARS"

In the end, isn't it companies chasing potental licensing profits in search of a sucker Commitee, Retinas be damned...

PS. Wayne- there's an inexpensive solution for colorists- simply use the 3D glasses collecting dust as sunglasses
... I hear that every HDR Screen sold will include a 4pk set of exchangeable lenses ;-)

I bid you a good night...

 

[Hrvoje Simic]

The world is often very bright and we don't see people complaining about it.

INT, Night, bedroom

John puts his son to bed.

CUT TO

EXT, Beach

People play beach volley ball on a bright summer day (HH shots)


...


Flashback sequence

John goes through rapid introspection with tunnel scene, beach scene, bedroom scene, desert scene, basement scene, stadium scene.

 

[Simon Dunne]

BT.2020 defines the gamut, which is wide, and 3x3 matrix to convert from and to RGB, it has nothing to do with HDR.

This is why i posted originally Stacey. What exactly is HDR? BT.2020 will give us a much large colour gamut, greater than P3, which is the current cinema standard for DCP's. So UHD is potentially going to give the consumer a better picture at home on Blu-Ray than they'll be able to watch in the cinema?! I'm having trouble understanding all this.........!!!

I like the comments about brightness, that will need to be tested for sure. I always have a back light behind my monitor to help balance my eyes to stop them getting light shocks.

 

[Gavin Greenwalt]

INT, Night, bedroom

John puts his son to bed.

CUT TO

EXT, Beach

People play beach volley ball on a bright summer day (HH shots)


...


Flashback sequence

John goes through rapid introspection with tunnel scene, beach scene, bedroom scene, desert scene, basement scene, stadium scene.

INT, Post House

Colorist slowly increases exposure of HDR effect over 30 seconds to give people a chance to adjust.

EXT, Film Set

Maybe the director wants people to be uncomfortable for an emotional effect.

 

[Hrvoje Simic]

INT, Post House

Colorist slowly increases exposure of HDR effect over 30 seconds to give people a chance to adjust.

EXT, Film Set

Maybe the director wants people to be uncomfortable for an emotional effect.

First scene changes storytelling language, affects scene context/emotion and introduces one more technological factor to cope with in already bombed post workflow.

Second scene abuses viewer's eyesight due to a creative whim and pushes viewers out of theaters.

 

[Wayne Morellini]

The world is often very bright and we don't see people complaining about it.

Why do you think people have sunglasses, squint, don't like going out at mid day in brighter latitudes, old movie makers huddle away from brighter periods of brighter days. Why the movie industry rarely uses brighter images, it is a special effect to make you uncomfortable the exact opposite of the movie going experience they want that most people will go to.

Time to update the dictionary...
PS. Wayne- there's an inexpensive solution for colorists- simply use the 3D glasses collecting dust as sunglasses
... I hear that every HDR Screen sold will include a 4pk set of exchangeable lenses ;-)

I bid you a good night...

He, he John, I wasn't going to say sunglasses because I knew people around here would jump on me protesting how it would adjust the color. Even turning the brightness down without glasses can adjust the perception of color balance.