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What is HDR, anyway?

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Re: What is HDR, anyway?

#211

Post by kllrnohj »

frollogaston wrote: post #180
kllrnohj wrote: post #50

Earlier quoted context omitted.

> To me, HDR feels like the system is ignoring my screen brightness settings. On both Android & iOS/MacOS it's not that HDR is ignoring your screen brightness, but rather the brightness slider is controlling the SDR range and then yes HDR can exceed that, that's the singular purpose of HDR to be honest. All the other purported benefits of HDR are at best just about HDR video profiles and at worst just nonsense bullsh…

"On both Android & iOS/MacOS it's not that HDR is ignoring your screen brightness, but rather the brightness slider is controlling the SDR range and then yes HDR can exceed that" Doesn't this mean HDR is ignoring my brightness setting? Looking at the Mac color profiles, the default HDR has some fixed max brightness regardless of the brightness slider. And it's very bright, 1600 nits vs the SDR max of 600 nits. At lea…

> Doesn't this mean HDR is ignoring my brightness setting?

Not exactly because it is still being scaled by your brightness setting. As in, start playing an HDR video and then mess with the brightness slider. You will still see the HDR content getting dimmer/brighter.

It's easier to think about in Apple's EDR terms. 0.0-1.0 is the SDR range, and the brightness slider is changing what the nit value is of "1.0" - is it 100 nits? 300 nits? 50 nits? etc... HDR content (in theory) still has that same 0.0-1.0 portion of the range, and it's still being scaled. However it can exceed that 1.0. It's still being scaled, it's still "respecting" that slider. Just the slider wasn't a brightness limit as you're wanting it to be, but a 1.0 alignment point.

The problem comes when HDR content is disrespectful to that. When it just absolutely slams the brightness, pushing all of its content way past that 1.0 value. This is bad content, and unfortunately it's incredibly common in HDR media due in part to the fact that the original HDR specs are very incomplete and in part because it's a new loudness war.

Re: What is HDR, anyway?

#212

Post by hbn »

wirybeige wrote: post #86
kllrnohj wrote: post #12

Earlier quoted context omitted.

HDR gaming: Yes. HDR full screen content: Yes. HDR general desktop usage: No. In fact you'll probably actively dislike it to the point of just turning it off entirely. The ecosystem just isn't ready for this yet, although with things like the "constrained-high" concepts ( https://www.w3.org/TR/css-color-hdr-1/#the-dynamic-range-lim... ) this might, and hopefully does, change & improve to a more pleasing result Also t…

I use HDR for general usage, Windows ruins non-HDR content when HDR is enabled due to their choice of sRGB tf. Luckily every Linux DE has chosen to use the gamma 2.2 tf, and looks fine for general usage. I use a mini-led monitor, and its quite decent, except for starfields, & makes it very usable even in bright conditions, and HDR video still is better in bright conditions than the equivalent SDR video. https://githu…

Windows HDR implementation is janky as hell. For months after I got my monitor I couldn't take screenshots because they'd all appear completely blown out, like you cranked the brightness to 300%.

Eventually I did some digging and found there's a setting in Snipping Tool that just... makes screenshots work on HDR displays.

It also seems to add another layer of Your Desktop Trying To Sort Its Shit Out when launching a game that's full screen. Sometimes it's fine, but some games like Balatro will appear fine at first, but then when you quit back to the desktop everything is washed out. Sleeping my PC and waking it back up seems to resolve this.

I recently played through Armored Core VI, and it supports HDR, but whenever I adjust my volume the screen becomes washed out to display the volume slider. Screenshots and recordings also appear washed out in the resulting file.

Re: What is HDR, anyway?

#213

Post by munificent »

dahart wrote: post #185
munificent wrote: post #179

Earlier quoted context omitted.

Yes, Ansel Adams was using a camera to capture a scene that had high dynamic range. I don't see the confusion here.

HDR is not referring to the scene’s range, and it doesn’t apply to film. It’s referring superficially but specifically to a digital process that improves on 8 bits/channel RGB images. And one of the original intents behind HDR was to capture pixels in absolute physical measurements like radiance, to enable a variety of post-processing workflows that are not available to film.

"High dynamic range" is a phrase that is much older than tone mapping. I see uses of "dynamic range" going back to the 1920s and "high dynamic range" to the 1940s:

https://books.google.com/ngrams/graph?content=dynamic+range%...

You might argue that "HDR" the abbreviation refers to using tone mapping to approximate rendering high dynamic range imagery on lower dynamic range displays. But even then, the sentence in question doesn't use the abbreviation. It is specifically talking about a dynamic range that is high.

Dynamic range is a property of any signal or quantifiable input, including, say sound pressure hitting our ears or photons hitting an eyeball, film, or sensor.

Re: What is HDR, anyway?

#214

Post by arghwhat »

dahart wrote: post #168
arghwhat wrote: post #153

Earlier quoted context omitted.

Arguably, even considering HDR a distinct thing is itself weird an inaccurate. All mediums have a range, and they've never all matched. Sometimes we've tried to calibrate things to match, but anyone watching SDR content for the past many years probably didn't do so on a color-calibrated and brightness calibrated screen - that wouldn't allow you to have a brightness slider. HDR on monitors is about communicating conte…

This! Yes I think you’re absolutely right. The term “HDR” is in part kind of an artifact of how digital image formats evolved, and it kind of only makes sense relative to a time when the most popular image formats and most common displays were not very sophisticated about colors. That said, there is one important part that is often lost. One of the ideas behind HDR, sometimes, is to capture absolute values in physica…

Absolute is also a funny size. From the perspective of human visual perception, an absolute brightness only matters if the entire viewing environment is also controlled to the same absolute values. Visual perception is highly contextual, and we are not only seeing the screen.

It's not fun being unable to watch dark scenes during the day or evening in a living room, nor is vaporizing your retinas if the ambient environment went dark in the meantime. People want good viewing experience in the available environment that is logically similar to what the content intended, but that is not always the same as reproducing the exact same photons as the directors's mastering monitor sent towards their their eyeballs at the time of production.

Re: What is HDR, anyway?

#216

Post by mightysashiman »

redox99 wrote: post #210
mightysashiman wrote: post #190

I have a question: how can I print HDR? Is there any HDR printer + paper + display lighting setup? My hypothesis are the following: - Increase display lighting to increase peak white point + use a black ink able to absorb more light (can Vantablack-style pigments be made into ink?) => increase dynamic range of a printable picture - Alternatively, have the display lighting include visible light + invisible UV light, a…

You would need a very strong light surrounded by a darkish environent. I don't see a point in "HDR Paper" if you need to place it under a special light.

usecase: a photo exhibition that wants to show pictures in HDR = An HDR print setup (i.e. paper + appropriately controlled lighting).

Haven't you ever been to a photo exhibition ?

Re: What is HDR, anyway?

#217

Post by dahart »

arghwhat wrote: post #214
dahart wrote: post #168

Earlier quoted context omitted.

This! Yes I think you’re absolutely right. The term “HDR” is in part kind of an artifact of how digital image formats evolved, and it kind of only makes sense relative to a time when the most popular image formats and most common displays were not very sophisticated about colors. That said, there is one important part that is often lost. One of the ideas behind HDR, sometimes, is to capture absolute values in physica…

Absolute is also a funny size. From the perspective of human visual perception, an absolute brightness only matters if the entire viewing environment is also controlled to the same absolute values. Visual perception is highly contextual, and we are not only seeing the screen. It's not fun being unable to watch dark scenes during the day or evening in a living room, nor is vaporizing your retinas if the ambient enviro…

Yep, absolutely! ;)

This brings up a bunch of good points, and it tracks with what I was trying to say about conflating HDR processing with HDR display. But do keep in mind that even when you have absolute value images, that doesn’t imply anything about how you display them. You can experience large benefits with an HDR workflow, even when your output or display is low dynamic range. Assume that there will be some tone mapping process happening and that the way you map tones depends on the display medium and its capabilities, and on the context and environment of the display. Using the term “HDR” shouldn’t imply any mismatch or disconnect in the viewing environment. It only did so in the article because it wasn’t very careful about its terms and definitions.

Re: What is HDR, anyway?

#218

Post by chaboud »

Having come from professional video/film tooling in the 90's to today, it's interesting to see the evolution of what "HDR" means. I used to be a purist in this space, where SDR meant ~8 stops (powers of two) or less of dynamic range, and HDR meant 10+. Color primaries and transfer function mapping were things I spoke specifically about. At this point, though, folks use "HDR" to refer to combinations of things.

Around this, a bunch of practical tooling surfaced (e.g., hybrid log approaches to luminance mapping) to extend the thinking from 8-bit gamma-mapped content presenting ~8 stops of dynamic range to where we are now. If we get away from just trying to label everyting "HDR", there are some useful things people should familiarize with:

1. Color primaries: examples - SDR: Rec. 601, Rec. 709, sRGB. HDR: Rec. 2020, DCI-P3. The new color primaries expand the chromatic representation capabilities. This is pretty easy to wrap our heads around: https://en.wikipedia.org/wiki/Rec._2020

2. Transfer functions: examples - SDR: sRGB, BT.1886. HDR: Rec. 2100 Perceptual Quantizer (PQ), HLG. The big thing in this space to care about is that SDR transfer functions had reference peak luminance but were otherwise relative to that peak luminance. By contrast, Rec. 2100 PQ code points are absolute, in that each code value has a defined meaning in measurable luminance, per the PQ EOTF transfer function. This is a big departure from our older SDR universe and from Hybrid Log Gamma approaches.

3. Tone mapping: In SDR, we had the comfort of camera and display technologies roughly lining up in the video space, so living in a gamma/inverse-gamma universe was fine. We just controlled the eccentricity of the curve. Now, with HDR, we have formats that can carry tone-mapping information and transports (e.g., HDMI) that can bidirectionally signal display target capabilities, allowing things like source-based tone mapping. Go digging into HDR10+, Dolby Vision, or HDMI SBTM for a deep rabbit hole. https://en.wikipedia.org/wiki/Tone_mapping

So HDR is everything (and nothing), but it's definitely important. If I had to emphasize one thing that is non-obvious to most new entrants into the space, it's that there are elements of description of color and luminance that are absolute in their meaning, rather than relative. That's a substantial shift. Extra points for figuring out that practical adaptation to display targets is built into formats and protocols.

Re: What is HDR, anyway?

#219

Post by tshaddox »

arghwhat wrote: post #153
dahart wrote: post #123

It seems like a mistake to lump HDR capture, HDR formats and HDR display together, these are very different things. The claim that Ansel Adams used HDR is super likely to cause confusion, and isn’t particularly accurate. We’ve had HDR formats and HDR capture and edit workflows since long before HDR displays. The big benefit of HDR capture & formats is that your “negative” doesn’t clip super bright colors and doesn’t…

Arguably, even considering HDR a distinct thing is itself weird an inaccurate. All mediums have a range, and they've never all matched. Sometimes we've tried to calibrate things to match, but anyone watching SDR content for the past many years probably didn't do so on a color-calibrated and brightness calibrated screen - that wouldn't allow you to have a brightness slider. HDR on monitors is about communicating conte…

The term "HDR" arguably makes more sense for the effect achieved by tone mapping multiple exposures of the same subject onto a "normal" (e.g. SRGB) display. In this case, the "high" in "HDR" just means "from a source with higher dynamic range than the display."

Re: What is HDR, anyway?

#220

Post by ignaloidas »

tart-lemonade wrote: post #102
sandofsky wrote: post #21

Earlier quoted context omitted.

While it isn't touched on in the post, I think the issue with feeds is that platforms like Instagram have no interest in moderating HDR. For context: YouTube automatically edits the volume of videos that have an average loudness beyond a certain threshold. I think the solution for HDR is similar penalization based on log luminance or some other reasonable metric. I don't see this happening on Instagram any time soon,…

> YouTube automatically edits the volume of videos that have an average loudness beyond a certain threshold. For anyone else who was confused by this, it seems to be a client-side audio compressor feature (not a server-side adjustment) labeled as "Stable Volume". On the web, it's toggleable via the player settings menu. https://support.google.com/youtube/answer/14106294 I can't find exactly when it appeared but the e…

Youtube has been long normalizing videos standard feed, switching to a -14 LUFS target in 2019. But LUFS is a global target, and is meant to allow higher peaks and troughs over the whole video, and the normalization does happen on a global level - if you exceed it by 3dB, then the whole video gets it's volume lowered by 3dB, no matter if the part is quiet or not.

The stable volume thing is meant to essentially level out all of the peaks and troughs, and IIRC it's actually computed server-side, I think yt-dlp can download stable volume streams if asked to.

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