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What is HDR, anyway?

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Re: What is HDR, anyway?

#201

Post by dahart »

pavlov wrote: post #195
dahart wrote: post #189

Earlier quoted context omitted.

They didn’t call that “HDR” at the time, and it wasn’t based on the idea of recording radiance or other absolute physical units. I’m certain physicists had high range digital cameras before Cineon, and they were working in absolute physical metrics. That would be a stronger example. You bring up an important point that is completely lost in the HDR discussion: this is about color resolution at least as much as it’s a…

It certainly was called HDR when those Cineon files were processed in a linear light workflow. And film was the only capture source available that could provide sufficient dynamic range, so IMO that makes it “HDR”. But I agree that the term is such a wide umbrella that almost anything qualifies. Fifteen years ago you could do a bit of superwhite glows and tone mapping on 8-bpc and people called that look HDR.

Do you have any links from 1990ish that show use of “HDR”? I am interested in when “HDR” became a phrase people used. I believe I remember hearing it first around 1996 or 97, but it may have started earlier. It was certainly common by 2001. I don’t see that used as a term nor an acronym in the Cineon docs from 1995, but it does talk about log and linear spaces and limiting the dynamic range when converting. The Cineon scanner predates sRGB, and used gamma 1.7. https://dotcsw.com/doc/cineon1.pdf

This 10 bit scanner gave you headroom of like 30% above white. So yeah it qualifies as a type of high dynamic range when compared to 8 bit/channel RGB, but on the other hand, a range of [0 .. 1.3] isn’t exactly in the spirit of what “HDR” stands for. The term implicitly means a lot more than 1.0, not just a little. And again people developing HDR like Greg Ward and Paul Debevec were arguing for absolute units such as luminance, which the Cineon scanner does not do.

Re: What is HDR, anyway?

#202

Post by dahart »

altairprime wrote: post #197
dahart wrote: post #189

Earlier quoted context omitted.

They didn’t call that “HDR” at the time, and it wasn’t based on the idea of recording radiance or other absolute physical units. I’m certain physicists had high range digital cameras before Cineon, and they were working in absolute physical metrics. That would be a stronger example. You bring up an important point that is completely lost in the HDR discussion: this is about color resolution at least as much as it’s a…

It was called "extended dynamic range" by ILM when they published the OpenEXR spec (2003): > OpenEXR (www.openexr.net), its previously proprietary extended dynamic range image file format, to the open source community https://web.archive.org/web/20170721234341/http://www.openex... And "larger dynamic range" by Rea & Jeffrey (1990): > With γ = 1 there is equal brightness resolution over the entire unsaturated image at…

As I remember it, Paul Debevec had borrowed Greg Ward’s RGBE file format at some point in the late 90s and rebranded it “.hdr” for his image viewer tool (hdrView) and code to convert a stack of LDR exposures into HDR. I can see presentations online from Greg Ward in 2001 that have slides with “HDR” and “HDRI” all over the place. So yeah the term definitely must have started in the late 90s if not earlier. I’m not sure it was as there in the early 90s though.

Re: What is HDR, anyway?

#203

Post by jrapdx3 »

Demiurge wrote: post #156
QuantumGood wrote: post #140

Earlier quoted context omitted.

Adams adjusted heavily with dodging and burning, even working to invent a new chemical process to provide more control when developing. He was great at determining exposure for his process as well. A key skill was having a vision for what the image would be after adjusting. Adams talked a lot about this as a top priority of his process.

> It's even more incredible that this was done on paper, which has even less dynamic range than computer screens! I came here to point this out. You have a pretty high dynamic range in the captured medium, and then you can use the tools you have to darken or lighten portions of the photograph when transferring it to paper.

Indeed so. Printing on paper and other substrates is inherently subtractive in nature which limits the gamut of colors and values that can be reproduced. Digital methods make the job of translating additive to subtractive media easier vs. the analog techniques available to film photographers. In any case, the image quality classic photography was able to achieve is truly remarkable.

Notably, the dodging and burning used by photographers aren't obsolete. There's a reason these tools are included in virtually every image-editing program out there. Manipulating dynamic range, particularly in printed images, remains part of the craft of image-making.

Re: What is HDR, anyway?

#205

Post by dahart »

levidos wrote: post #196
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…

Is there a difference in capturing in HDR vs RAW?

Good question. I think it depends. They are kind of different concepts, but in practice they can overlap considerably. RAW is about using the camera’s full native color resolution, and not having lossy compression. HDR is overloaded, as you can see from the article & comments, but I think HDR capture is conceptually about expressing brightness in physical units like luminance or radiance, and delaying the ‘exposure’ until display time. Both RAW and HDR typically mean using more than 8 bits/channel and capturing high quality images that will withstand more post-processing than ‘exposed’ LDR images can handle.

Re: What is HDR, anyway?

#206

Post by altairprime »

dahart wrote: post #202
altairprime wrote: post #197

Earlier quoted context omitted.

It was called "extended dynamic range" by ILM when they published the OpenEXR spec (2003): > OpenEXR (www.openexr.net), its previously proprietary extended dynamic range image file format, to the open source community https://web.archive.org/web/20170721234341/http://www.openex... And "larger dynamic range" by Rea & Jeffrey (1990): > With γ = 1 there is equal brightness resolution over the entire unsaturated image at…

As I remember it, Paul Debevec had borrowed Greg Ward’s RGBE file format at some point in the late 90s and rebranded it “.hdr” for his image viewer tool (hdrView) and code to convert a stack of LDR exposures into HDR. I can see presentations online from Greg Ward in 2001 that have slides with “HDR” and “HDRI” all over the place. So yeah the term definitely must have started in the late 90s if not earlier. I’m not sur…

Oo, interesting! That led me to this pair of sentences:

"Making global illumination user-friendly" (Ward, 1995) https://radsite.lbl.gov/radiance/papers/erw95.1/paper.html

> Variability is a qualitative setting that indicates how much light levels vary in the zone, i.e. the dynamic range of light landing on surfaces.

> By the nature of the situation being modeled, the user knows whether to expect a high degree of variability in the lighting or a low one.

Given those two phrases, 'a high or low degree of variability in the lighting' translates as 'a high or low degree of dynamic range' — or would be likely to, given human abbreviation tendencies, in successive works and conversations.

Re: What is HDR, anyway?

#207

Post by kllrnohj »

LinAGKar wrote: post #191
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…

>HDR can exceed that It's not just the HDR content that gets brighter, but SDR content too. When I test it in Chrome on Android, if an HDR image shows up on screen the phone start overriding the brightness slider completely and making everything brighter, including the phone's system UI. >The only thing HDR actually does is allow for brighter colors vs. SDR. Not just brighter, but also darker, so it can preserve deta…

> It's not just the HDR content that gets brighter, but SDR content too. When I test it in Chrome on Android, if an HDR image shows up on screen the phone start overriding the brightness slider completely and making everything brighter, including the phone's system UI.

You have an "old" style handling of HDR on Android. Newer/better devices don't do that (specifically those that support https://source.android.com/docs/core/display/mixed-sdr-hdr )

Similarly MacOS/iOS doesn't do that.

> Not just brighter, but also darker, so it can preserve detail in dark areas rather than crushing them.

It does not get darker, and while PQ allocates more bits to the dark region HLG does not. And, more importantly, neither does the actual display panel which are still typically gamma 2.2-2.4 regardless. So PQ's extra precision in the dark areas is ~never utilized other than as tonemapping input, but the resulting output does not have any increased precision in the darks over SDR.

In fact it actually has less precision in the dark areas as the increased display luminance range means the panels native bit depth need to cover more range.

Re: What is HDR, anyway?

#208

Post by haswell »

mrandish wrote: post #158
sandofsky wrote: post #59

Earlier quoted context omitted.

> Does anyone else find the hubris in the first paragraph writing as off-putting as I do? > "we finally explain what HDR actually means" No. Because it's written for the many casual photographers we've spoken with who are confused and asked for an explainer. > Then spends 2/3rds of the article on a tone mapping expedition, only to not address the elephant in the room, that is the almost complete absence of predictabl…

> That's because this post is about HDR It's about HDR from the perspective of still photography, in your app, on iOS, in the context of hand-held mobile devices. The post's title ("What Is HDR, Anyway?"), content level and focus would be appropriate in the context of your company's social media feeds for users of your app - which is probably the audience and context it was written for. However in the much broader co…

> However in the much broader context of HN, a highly technical community whose interests in imaging are diverse, the article's content level and narrow focus aren't consistent with the headline title. It seems written at a level appropriate for novice users.

That is hardly the fault of the authors though. The article seems entirely appropriate for its intended audience, and they can’t control who posts it on a site like HN.

Re: What is HDR, anyway?

#209

Post by colechristensen »

zamadatix wrote: post #139
colechristensen wrote: post #73

Earlier quoted context omitted.

I have a screen which is "HDR" but what that means is when you turn the feature on it just makes everything more muted, it doesn't actually have any more dynamic range. When you turn HDR on for a game it basically just makes most things more muddy grey. I also have a screen which has a huge gamut and blows out colors in a really nice way (a bit like the aftereffects of hallucinogens, it has colors other screens just…

The cheap displays adding broken HDR400 support destroyed so much public opinion on HDR. Not actually providing a wider range but accepting the HDR signal would at least have been a minor improvement if the tone mapping weren't completely broken to the point most people just associate HDR with a washed out picture.

>The cheap displays adding broken HDR400 support destroyed so much public opinion on HDR.

It's funny because the display I have that does this was a relatively premium Odyssey G7 which at $700 isn't at all a cheap monitor. (I like it, it's just not at all HDR, or at least not perceivably so compared to Apple devices and an OLED TV)

Re: What is HDR, anyway?

#210

Post by redox99 »

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.
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