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Comment by unfocussed_mike | Hacker News Reader

How is it not from a lack of dynamic range?

Colour transparency film (e.g. Fuji Velvia -- RVP50) shows the same thing as clearly.

You basically can't map real world light into the dynamic range of a typical camera without causing some of this experience, can you?

The question is how you determine how dark shadows should be -- your brain is doing a lot of work to hide from you the tricks it uses to make shadows appear less dark than they might be with a linear response.

Or even how they would look with a non-linear response that is even across the "frame"; your brain is doing localised dodge/burn type work, constantly.

Camera manufacturers have "tastemakers" for this stuff on digital, just as film manufacturers used to have them for film.

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It is different because it is obvious that shadows are darker than in reality while highlights are much brighter than in reality.

Any brain filtering would have to affect the photos as well, even if it was true.

No common image format uses linear response. It would explain this problem if cameras treat them as linear.

Maybe they should just make the cameras take physically correct colors, instead of relying on people, as the typical person will always choose extreme contrast that will make the camera unusable. (and can be easily increased in editing)

> Any brain filtering would have to affect the photos as well, even if it was true.

Not when the dynamic range of reality is much greater than that of photographs, and your visual system is one of the best visual processors in existence. It’s like reducing a 24-bit image to 16-bit - the image is “good enough” to identify the subject, but it is quite lossy. Photography itself is a lossy process.

What is "brain filtering" and why would you think either film or digital can reproduce the same visual effect as our eyes see?

Our brain does a perceptual aggregation of multiple frames and inputs. This is not how cameras work.

Also "make cameras take physically correct colors" is impossible unless you're talking about spectral capture, which is orders if magnitudes more complex. If you're using just RGB photosites AND RGB displays, there is no such thing as physically correct colors. Everything will just be a mapping at best, with the best that color science experts can actually provide.

The one I was replying to talked about brain processing. Whatever it is doesn't need to and shouldn't be reproduced in photography as the protograph gets processed just like everything else when you look at it.

Reality --> eye --> "brain filter"

Reality --> photo --> eye -> "brain filter"

Cameras should only record the colors as accurately as possible. Or if you want to nitpick again, so that the photo stimulates the eye receptors identically to whatever was captured.

they already do that to the best of our abilities.

Color is incredibly complex. It's easy to say "we should capture it as accurately as possible" but I don't think you fully comprehend the high complexity involved.

Your concept of matching eye receptors is wrong too. Color is perceptual and subjective. Your perception of color is based on your upbringing, your genetics, your environment, your own mental faculties, your mental state etc... What is accurate? Your eyes see some spectral energy, your rods and cones convert those to signals, your brain then adds that into an aggregate set of information that it's constantly infilling and, most importantly, guessing about.

You can't guarantee that multiple people see color the same.

Now even if a camera could hypothetically capture an image accurately to the real world (IMHO only possible with a hypothetical full spectrum sensor), how would you store it? The second you convert it to RGB data it needs a perceptual conversion to the bit depth of the data format. Now even if you have a file format that can efficiently represent this, you'd also need full spectrum displays so that we could beam that exact color to your retinas.

Color science is incredibly complex. You're trying to trivialize it into matching your own narrow perception of color.

It's physically impossible for a photo to send the same photons into the eye as the original scene did - imagine taking a photo outdoors in sunlight and then viewing that photo indoors, the whitest possible parts of the photo will be literally orders of magnitude darker than the original scene. Similarly you can't reproduce the same colours because you don't have all of the colours available (e.g. there's no way a computer screen using RGB pixels can reproduce the precise wavelength that a sodium lamp gives out). Trying to reproduce the experience of viewing the original scene is the best we can do, and that requires not just physics but biology and psychology. You talk about "eye receptors", but the line where the eye ends and the brain begins is actually very fuzzy - ontogenically your eyes are part of your brain, and the signals passing from eyes to brain are already in a "compressed form" where e.g. a straight line is represented by a single nerve impulse.

This explains really well several things I was struggling to explain.

And also introduced me to the word "ontogenically". Thanks twice.

If you have never done this before, I absolutely recommend -- while it is still possible to do this in a practical way -- getting a cheap film camera, getting hold of a proper incident light meter (like a Sekonic L-208 or L-308), and shooting some Fuji Velvia 50 or Provia 100F. Or if you can find it, some modern Ektachrome.

For example you might want to go to a beach or a park and shoot throughout the day on a bright day. Put people or objects in the foreground and then shoot them with either the light behind you or in front. Use the incident metering dome to meter the light

(you'll need to look this up, but the broad point of it is you stand in the same light as your subject and point the meter into the light, rather than at your subject)

Once you see what transparency film does in high-contrast situations I think you'll better understand what I'm trying to get across.

I don't think shadows are darker than in reality, but instead don't have their detail captured, or get swamped out by high black levels on screens or glare in the viewing environment. Also highlights get clipped at a much lower level than in reality (photographs of suns aren't eye-searing unlike the real thing).

There's something off about the brightness sensitivity curves, if I can dial shadow controls way way up and salvage an otherwise botched, underexposed photo, why is it that I have to do so manually?

The dynamic range is clearly there. And we're not talking about such ridiculous values that the sensor noise becomes prominent.

> why is it that I have to do so manually?

You can do that correction in that situation because you've looked at the image, you know what it is meant to be, and you can decide on a set of adjustments that produce something that approximates what you want, perceptually.

But without truly extensive scene knowledge, cameras can't do that automatically, and they also can't know what information that is important to the photographer that they'd be affecting if they did.

Cameras have to try to ascertain what would be middle grey in a scene and then apply a general purpose tone curve to an image, but they do not know what is in the scene.

They can't even know for sure if the photo they are being asked to take is properly exposed by any absolute definition, in fact.

[I cut out a lot of this because I don't think it's going to be easy to complete the explanation here]

No, the problem is VERY OBVIOUSLY more severe than that. It's really as if the images were treated as linear, which they are not. (they use gamma correction)

Honestly, whatever your understanding is here, you should probably build a demonstration to get it across to people.

Have you ever shot photographs with a colour transparency film?

This is also incorrect and trivializing of the color science. Images may use gamma correction, they may not. Trying to describe it in terms of gamma is like trying to describe food in terms of saltiness alone. You're ignoring tons of other factors.

Any image being displayed, or encoded in a standard such as sRGB, is using gamma. It is not optional.

Sure, and any meal you eat will have a salt content (possibly zero). Doesn't mean that that tells you all the things that could be wrong or right about the meal.

No. It isn't there so that you can use it when you choose to. All devices expect it to be used. When you skip it the colors will be wrong.

You're missing the point. You can't ONLY describe color spaces in gamma differences.

Gamma is just a single element of a color space. The whole trivializing sRGB into being a 2.2 Gamma versus linear is an over simplification that ignores gamut , white point, bit depth and more.

That's my point. You're trivializing what color is because you clearly have not dealt with it at scale.

No I'm not doing that, there seems to be some problem specifically there. Either the values are converted incorrectly, or not at all, effectivelly stretching about 8 fstops into the 11.6 (slightly less for video) f-stops of sRGB.

You can download an alternate color scheme from Technicolor for Canon cameras that makes the colors appear fairly reasonable.

"makes the colors appear fairly reasonable"

From what color space to what color space, and what display or print type?

Now you're back to describing a average case perceptual color rather than your initial point of accuracy.

I meant using gamma as a conversion function. There's a whole world of color transformations outside of just gamma. Gamma is just one of many transformations, and you can have two color spaces with identical gamma transforms, but different gamuts, white points etc...

I think a lot of people were misunderstanding my comment. I never meant to imply that gamma is the only important consideration in color perception, I was only reacting to the statement that it was optional. Even color spaces that don't use gamma (i.e. are linear) must have a gamma applied before you can view them.

https://xkcd.com/386/

gamma correction is compression, sacrificing data in regions where the eye is less sensitive for more precision in the sensitive ranges. images would look the same without it, you'd just be wasting bits encoding differences that the eye can't see

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