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What is HDR, anyway?

(www.lux.camera)
790 points _kush | 2 comments | 14 May 25 12:46 UTC | HN request time: 0.514s | 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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1. altairprime ◴[14 May 25 19:25 UTC] No.43988277[source]▶
The digital process of tonemapping, aka. 'what Apple calls Smart HDR processing of SDR photos to increase perceptual dynamic range', can be applied to images of any number of channels of any bit depth — though, if you want to tonemap a HyperCard dithered black-and-white image, you'll probably have to decompile the dithering as part of creating the gradient map. Neither RGB nor 8-bit are necessary to make tonemapping a valuable step in image processing.
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2. dahart ◴[14 May 25 19:44 UTC] No.43988441[source]▶
That’s true, and it’s why tonemapping is distinct from HDR. If you follow the link from @xeonmc’s comment and read the comments, the discussion centers on the conflation of tonemapping and HDR.

https://news.ycombinator.com/item?id=43987923

That said, the entire reason that tonemapping is a thing, and the primary focus of the tonemapping literature, is to solve the problem of squeezing images with very wide ranges into narrow display ranges like print and non-HDR displays, and to achieve a natural look that mirrors human perception of wide ranges. Tonemapping might be technically independent of HDR, but they did co-evolve, and that’s part of the history.