What is HDR, anyway?

> The sentence “What if I told you that analog photographers captured HDR as far back as 1857?” is explicitly claiming that analog photographers use “HDR” capture,

No, it isn't. It's saying they captured HDR scenes.

> The result of the juxtaposition is that the article did in fact claim Adams used HDR

You can't "use" HDR. It's an adjective, not a noun.

> Film’s 12 stops is not really “high” range by HDR standards, and a little exposure latitude isn’t where “HDR” came from.

The Reinhard tone mapper, a benchmark that regularly appears in research papers, specifically cites Ansel Adams as inspiration.

"A classic photographic task is the mapping of the potentially high dynamic range of real world luminances to the low dynamic range of the photographic print."

https://www-old.cs.utah.edu/docs/techreports/2002/pdf/UUCS-0...

> Perhaps it’s useful to reflect on the fact that HDR has a counterpart called LDR that’s referring to 8 bits/channel RGB.

8-bits per channel does not describe dynamic range. If I attach an HLG transfer function on an 8-bit signal, I have HDR. Furthermore, assuming you actually meant 8-bit sRGB, nobody calls that "LDR." It's SDR.

> Analog cameras have exposure control and thus can capture any range you want.

This sentence makes no sense.

Sorry man, you seem really defensive, I didn’t mean to put you on edge. Okay, if you are calling the scenes “HDR” then I’m happy to rescind my critique about Ansel Adams and switch instead to pointing out that “HDR” doesn’t refer to the range of the scene, it refers to the range capability of a digital capture process. I think the point ultimately ends up being the same either way. Hey where is HDR defined as an adjective? Last time I checked, “range” could be a noun, I think… no? You must be right, but FWIW, you used HDR as a noun in your 2nd to last point… oh and in the title of your article too.

Hey it’s great Reinhard was inspired by Adams. I have been too, like a lot of photographers. And I’ve used the Reinhard tone mapper in research papers, I’m quite familiar with it and personally know all three authors of that paper. I’ve even written a paper or maybe two on color spaces with one of them. Anyway, the inspiration doesn’t change the fact that 12 stops isn’t particularly high dynamic range. It’s barely more than SDR. Even the earliest HDR formats had like 20 or 30 stops, in part because the point was to use physical luminance instead of a relative [0..1] range.

8 bit RGB does sort-of in practice describe a dynamic range, as long as the 1 bit difference is approximately the ‘just noticeable difference’ or JND as some researchers call it. This happens to line up with 8 bits being about 8 stops, which is what RGB images have been doing for like 50 years, give or take. While it’s perfectly valid arithmetic to use 8 bits values to represent an arbitrary amount like 200 stops or 0.003 stops, it’d be pretty weird.

Plenty of people have called and continue to call 8 bit images “LDR”, here’s just three of the thousands of uses of “LDR” [1][2][3], and LDR predates usage of SDR by like 15 years maybe? LDR predates sRGB too, I did not actually mean 8 bit sRGB. LDR and SDR are close but not quite the same thing, so feel free to read up on LDR. It’s disappointing you ducked the actual point I was making, which is still there even if you replace LDR with SDR.

What is confusing about the sentence about analog cameras and exposure control? I’m happy to explain it since you didn’t get it. I was referring to how the aperture can be adjusted on an analog camera to make a scene with any dynamic range fit into the ~12 stops of range the film has, or the ~8 stops of range of paper or an old TV. I was just trying to clarify why HDR is an attribute of digital images, and not of scenes.

[1] https://www.easypano.com/showkb_228.html#:~:text=The%20Dynam...

[2] https://www.researchgate.net/figure/shows-digital-photograph...

[3] https://irisldr.github.io/

You opened this thread arguing that Ansel Adams didn't "use HDR." I linked you to a seminal research paper which argues that he tone mapped HDR content, and goes on to implement a tone mapper based on his approach. This all seems open and shut.

> I’m happy to rescind my critique about Ansel Adams

Great, I'm done.

> and switch instead to pointing out that “HDR” doesn’t refer to the range of the scene

Oh god. Here's the first research paper that popped into my head: https://static.googleusercontent.com/media/hdrplusdata.org/e...

"Surprisingly, daytime shots with high dynamic range may also suffer from lack of light."

"In low light, or in very high dynamic range scenes"

"For high dynamic range scenes we use local tone mapping"

You keep trying to define "HDR" differently than current literature. Not even current— that paper was published in 2016! Hey, maybe HDR meant something different in the 1990s, or maybe it was just ok to use "HDR" as shorthand for when things were less ambiguous. I honestly don't care, and you're only serving to confuse people.

> the aperture can be adjusted on an analog camera to make a scene with any dynamic range fit into the ~12 stops of range the film has, or the ~8 stops of range of paper or an old TV.

You sound nonsensical because you keep using the wrong terms. Going back to your first sentence that made no sense:

> Analog cameras have exposure control and thus can capture any range you want

You keep saying "range" when, from what I can tell, you mean "luminance." Changing a camera's aperture scales the luminance hitting your film or sensor. It does not alter the dynamic range of the scene.

Analog cameras cannot capture any range. By adjusting camera settings or attaching ND filters, you can change the window of luminance values that will fit within the dynamic range of your camera. To say a camera can "capture any range" is like saying, "I can fit that couch through the door, I just have to saw it in half."

> And I’ve used the Reinhard tone mapper in research papers, I’m quite familiar with it and personally know all three authors of that paper. I’ve even written a paper or maybe two on color spaces with one of them.

I'm sorry if correcting you triggers insecurities, but if you're going to make an appeal to authority, please link to your papers instead of hand waving about the people you know.

Hehe outside is “HDR content”? To me that still comes off as confused about what HDR is. I know you aren’t, but that’s what it sounds like. A sunny day has a high dynamic range for sure, but the acronym HDR is a term of art that implies more than that. Your article even explains why.

Tone mapping doesn’t imply HDR. Tone mapping is always present, even in LDR and SDR workflows. The paper you cited explicitly notes the idea is to “extend” Adams’ zone system to very high dynamic range digital images, more than what Adams was working with, by implication.

So how is a “window of luminance values” different from a dynamic range, exactly? Why did you make the incorrect and obviously silly assumption that I was suggesting a camera’s aperture changes the outdoor scene’s dynamic range rather than what I actually said, that it changes the exposure? Your description of what a camera does is functionally identical. I’m kinda baffled as to why you’re arguing this part that we both understand, using hyperbole.

I hope you have a better day tomorrow. Good luck with your app. This convo aside, I am honestly rooting for you.

> Hehe outside is “HDR content”? To me that still comes off as confused about what HDR is.

"Surprisingly, daytime shots with high dynamic range may also suffer from lack of light."

That's from, "Burst photography for high dynamic range and low-light imaging on mobile cameras," written by some of the most respected researchers in computational photography. It has 342 citations according to ACM.

I'm still waiting for a link to your papers.

> Tone mapping doesn’t imply HDR.

https://en.wikipedia.org/wiki/Tone_mapping

First sentence: "Tone mapping is a technique used in image processing and computer graphics to map one set of colors to another to approximate the appearance of high-dynamic-range (HDR) images in a medium that has a more limited dynamic range."

> Why did you make the incorrect and obviously silly assumption that I was suggesting a camera’s aperture changes the outdoor scene’s dynamic range rather than what I actually said, that it changes the exposure?

Because you keep bumbling details like someone with a surface level understanding. Your replies are irrelevant, outdated, or flat out wrong. It all gives me flashbacks to working under engineers-turned-managers who just can't let go, forcing their irrelevant backgrounds into discussions.

It's cool that you studied late 90s 3D rendering. So did I. It doesn't make you an expert in computational photography. Please stop confusing people with your non-sequiturs.

What does the lack of light quote prove? That’s a statement about color resolution, not range, and it uses “high dynamic range” and not “HDR content”. I think you’ve missed my point and are not listening.

Yes tone mapping is used on HDR images. It just doesn’t imply HDR. SDR gamma is tone mapping, for example, which the Wikipedia link you sent explains. Your claim is that Adams use of tone mapping is evidence that he is capturing “HDR content”. The paper you sent doesn’t use that language, it doesn’t ever say Adams was doing tone mapping, it says they develop a tone mapping method inspired by Adams’ zone system that extends the idea into higher dynamic range.

You’re using your own misunderstanding and mis-interpretation of my comments as evidence that they’re wrong. Hey I totally might be wrong about a lot of things, and sure maybe I’m completely non-sensical, but you certainly haven’t convinced me of that. I haven’t had trouble speaking with other people about HDR imaging, people who are HDR experts. All I’m getting out of this so far is that some people react very badly to any hint of critique.

From my perspective, I’m also only hearing bumbling errors, errors like that HDR is an adjective, that LDR doesn’t exist and nobody uses it, that using “range” is incorrect when I say it but not when you do and “window of luminance values” is better, and that Ansel Adams was doing HDR imaging.

Ben, we’re having a bona-fide miscommunication, and I wanted to fix it but I’m failing, and it feels like you’re determined not to fix it or find any common ground. In another environment we’d probably be having a friendly, productive and enlightening conversation. I’m sure there are some things I could learn from you.