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What is HDR, anyway?

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791 points _kush | 1 comments | 14 May 25 12:46 UTC | HN request time: 1.207s | source
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dahart ◴[14 May 25 16:48 UTC] No.43986653[source]▶
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 lose color resolution in super dark color. As a photographer, with HDR you can re-expose the image when you display/print it, where previously that wasn’t possible. Previously when you took a photo, if you over-exposed it or under-exposed it, you were stuck with what you got. Capturing HDR gives the photographer one degree of extra freedom, allowing them to adjust exposure after the fact. Ansel Adams wasn’t using HDR in the same sense we’re talking about, he was just really good at capturing the right exposure for his medium without needing to adjust it later. There is a very valid argument to be made for doing the work up-front to capture what you’re after, but ignoring that for a moment, it is simply not possible to re-expose Adams’ negatives to reveal color detail he didn’t capture. That’s why he’s not using HDR, and why saying he is will only further muddy the water.

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munificent ◴[14 May 25 17:54 UTC] No.43987388[source]▶
> The claim that Ansel Adams used HDR is super likely to cause confusion

That isn't what the article claims. It says:

"Ansel Adams, one of the most revered photographers of the 20th century, was a master at capturing dramatic, high dynamic range scenes."

"Use HDR" (your term) is vague to the point of not meaning much of anything, but the article is clear that Adams was capturing scenes that had a high dynamic range, which is objectively true.

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dahart ◴[14 May 25 18:04 UTC] No.43987469[source]▶
Literally the sentence preceding the one you quoted is “What if I told you that analog photographers captured HDR as far back as 1857?”.
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munificent ◴[14 May 25 18:56 UTC] No.43988031[source]▶
Yes, Ansel Adams was using a camera to capture a scene that had high dynamic range.

I don't see the confusion here.

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dahart ◴[14 May 25 19:04 UTC] No.43988110[source]▶
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.
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munificent ◴[14 May 25 21:01 UTC] No.43989172[source]▶
"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.

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1. samplatt ◴[15 May 25 04:11 UTC] No.43991774[source]▶
To further complicate the issue, "high dynamic range" is a phrase that will come up across a few different disciplines, not just related to the capture & reproduction of visual data.