[HN Gopher] Why dark and light is complicated in photographs
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Why dark and light is complicated in photographs
Author : smbv
Score : 91 points
Date : 2022-03-13 15:29 UTC (7 hours ago)
(HTM) web link (aaronhertzmann.com)
(TXT) w3m dump (aaronhertzmann.com)
| whoisburbansky wrote:
| The tone of the article stands out to me; not much in the way of
| exaggeration or opinions on "the best" way to do a certain thing,
| but an almost dispassionate tour of some of the different ways
| we've thought about light and dark artistically, over time.
| Thoroughly enjoyed the read!
| twoWhlsGud wrote:
| Agree on the nice historical summary. The end of the final
| paragraph struck me in particular:
|
| "My photos are a collaboration between me and the algorithm
| designers and camera manufacturers, and they reflect a
| combination of aesthetic decisions made by each of us."
|
| The one downside of taking pictures with such a strongly
| opinionated technology is that your pictures are going to look
| like everyone else's (or increasingly just weird). Ansel Adams
| developed his darkroom technique over decades - and as the
| author mentions, applying them took hours of meticulous labor.
| So his output really did look different from most other
| peoples'.
|
| You can still differentiate your photographs on the basis on
| their subject matter, of course. But if everyone is shooting
| out of the same algorithmic pipeline, making your pictures look
| better technically is going to be increasingly hard. (And given
| current limitations, someone knowledgeable in the field today
| can still usually tell the difference between photographs taken
| with good lenses carefully deployed and cell phone output. But
| it's unclear how long that will be true.)
| goldenkey wrote:
| Lenses can be added to cell phones through 3rd party
| attachments. And aren't these ML options able to be turned
| off? It should make the phone camera much more like a
| standard camera.
| marban wrote:
| And one day you'll look back at all your Jpegs and wonder why you
| messed up all your memories with tasteless HDR effects.
| nyanpasu64 wrote:
| HDR capture (preserving more than 8 bits of light level,
| preserving meaningful detail in the shadows and not clipping
| highlights) preserves more of a scene than non-HDR JPEGs. Tone-
| mapping is the "tasteless HDR effect" which I have mixed
| feelings about (and can absolutely be done poorly, resulting in
| light halos around darker objects).
| antattack wrote:
| I'm surprised article claims that photography and film are no
| longer 'racist'. Most of my photos are underexposing dark
| complexions. It might be to do with limited dynamic range though,
| but still exists.
| Ma8ee wrote:
| Is it dark complexions or everything dark. It might be that it
| is only when it is a a face you notice the lack of details.
| wizzwizz4 wrote:
| "Racist" is being used metaphorically. The choice of film
| chemistry to use will affect what sort of faces are captured
| well, and what sort of faces are captured poorly.
| rkuska wrote:
| Roy DeCarava has one of the most beautifully developed prints
| of black people. Here is an interesting article on that subject
| https://www.nytimes.com/2015/02/22/magazine/a-true-picture-o...
| antiterra wrote:
| Talking about film is particularly complicated, as film does not
| have an entirely linear response to light. This is called
| reciprocity failure and means that you often need to expose way
| longer than 2x the time to have the effect of 2x the light.
|
| For digital, the data directly from camera sensors almost always
| needs some correction, de-mosaicing or massaging to generate an
| image viewable on a screen. This requires the camera to make what
| ends up being an aesthetic decision on what the photo looks like.
| Detail isn't just how bright or how dark, but also the available
| gradients in between. This means there are cases where the
| dynamic range is automatically expanded (instead of clipped) and
| contrast unnaturally increased in order to have a photo that
| isn't just mud.
|
| Ultimately, this means that technical considerations map directly
| to artistic ones, and there is no objectively correct image from
| sensor data. The idea that a 'no filter' picture conveys some
| kind of divine truth is a myth.
| leephillips wrote:
| Good point about the meaninglessness of a "no filter" concept.
| The article is very interesting in regard to lightness mapping,
| and there a another, related subject of hue mapping. This is a
| good part of the reason why pictures from different camera
| brands look different.
|
| Your description of reciprocity failure is not quite right. The
| idea is that if you double the time the shutter is open and
| also decrease the aperture by one stop, you should not change
| the amount of light hitting the film (you will change other
| things, of course). The overall brightness should be the same
| when you make these "reciprocal" adjustments. This does in fact
| hold pretty well within a certain range of shutter speeds.
| Reciprocity failure occurs at longer or smaller speeds, where
| the reciprocal relationship doesn't quite work.
| markdown wrote:
| Quite a topical article, considering the controversy around how
| they made a potentially great Batman movie unwatchable by turning
| large parts of it into a radio drama where you can't see anything
| and have to figure out what's happening with nothing but your
| ears.
| unfocussed_mike wrote:
| Oh this is the most perfect description of the second worst
| trend in cinema.
|
| The worst trend being loud music and mumbled dialogue that make
| it impossible to experience even as a radio drama.
| ElephantsMyAnus wrote:
| It seems to me there must be some kind of error in color
| calibration of most cameras. They make shadows much darker than
| they are, and bright areas much brighter than they are. It's not
| from a lack of dynamic range.
| unfocussed_mike wrote:
| 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.
| tomc1985 wrote:
| 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.
| unfocussed_mike wrote:
| > 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]_
| ElephantsMyAnus wrote:
| 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)
| wonnage wrote:
| 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
| unfocussed_mike wrote:
| 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?
| dagmx wrote:
| 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.
| ElephantsMyAnus wrote:
| 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)
| LocalH wrote:
| > 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.
| dagmx wrote:
| 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.
| ElephantsMyAnus wrote:
| 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.
| [deleted]
| dagmx wrote:
| 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.
| unfocussed_mike wrote:
| 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.
| nyanpasu64 wrote:
| 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).
| [deleted]
| user-the-name wrote:
| marban wrote:
| The error is the photographer. People just got used to ultra-
| correction of modern-day phone cams.
| Ma8ee wrote:
| That is exactly what is happening when you lack dynamic range.
|
| Say that your eye is sensitive from light intensity 0 to 100 in
| some units, but your camera sensor only handles 40 to 60. That
| means that everything under 40 will be mapped to black, and
| everything above 60 will be mapped to white.
| [deleted]
| ElephantsMyAnus wrote:
| No, that does not make any sense. That should result in 40,
| and everything darker resulting in 40, while 60 and
| everything brighter resulting in 60. But what you can see is
| that 40 results in 0, and 60 resulting in 100. That should
| never happen unless there is an error in processing.
|
| Only the picture file format should limit what range you can
| save with any modern camera.
| wizzwizz4 wrote:
| It does make sense. 40 is black, and 60 is white.
| ElephantsMyAnus wrote:
| No it doesn't make sense. You should not be able to
| capture anything darker than 40, or brighter than 60 if
| you are limited to 40-60. (actually by the file format,
| not the sensor, sensors today have higher dynamic ranges
| than 8 bit sRGB) It should not turn 40 into 0 and 60 into
| 100.
| wizzwizz4 wrote:
| In real life, a logarithmic brightness scale (which is
| how human perception works) goes from negative infinity
| (zero energy) to positive infinity (infinite energy) -
| excluding both endpoints. 0 is not the bottom, and 100 is
| not the top.
|
| In real life, photographs are printed on paper. The
| brightness of light reflecting off paper depends not only
| on the colour of the paper, but on the brightness of the
| illumination. (Likewise, photographs displayed on a
| computer monitor depend on the screen's brightness.)
|
| In real life, human brightness perception depends on the
| brightness of the environment. An LED can look bright in
| the dark and dim in sunlight, and range dim to medium to
| bright on a cloudy day without anyone really noticing
| that the clouds between them and the sun are thicker or
| thinner.
|
| In real life, there _is_ no 0. There _is_ no 100. _Your
| comment_ doesn 't make any sense.
| unfocussed_mike wrote:
| Right. Metering is even now with scene programs and AI
| still basically a complicated negotiation about
| establishing middle grey -- when there may be no
| perceptual middle grey in the scene at all (black cat in
| coal bin, polar bear in snow)
|
| The narrow band of sensitivity of a film or sensor has to
| be sort of moved to where it is needed (by controlling
| how much light gets in or for how long) according to the
| result _the photographer is likely to want from their
| photo_.
|
| Even the most basic of film dead-reckoning methods --
| Sunny 16 -- relies on subjective input from the
| photographer:
|
| https://en.wikipedia.org/wiki/Sunny_16_rule
|
| And it's up against the nature of human perception of
| light and dark, which as this classic page demonstrates,
| is complex:
|
| https://scienceinfo.net/video-chessboard-illusion-
| confuses-p...
| ubercow13 wrote:
| It's trivial to take an image editor and any existing
| image that is as you describe, and adjust the black point
| to 40 "percent" and white to 60%. It won't look more
| correct or realistic at all.
| Ma8ee wrote:
| That of course depends on how you show it on the screen.
| You can of course show those part of the sensor that didn't
| register anything (less than 40) as grey, and everything
| than saturated the sensor as a bit lighter grey. But people
| don't tend to like the look of those pictures very much,
| and they definitely don't look more natural than the
| conventional processing.
|
| The main limitation isn't the file format. The main
| limitation is the sensor. On the lower end, it is noise in
| different forms that overwhelm the very weak signal from
| dark areas. On the higher end, the sensors get saturated,
| that is, the semi-conductor bucket for the charges that is
| released by the photons get full.
|
| And then the experience of the picture is of course limited
| by the medium that is used to display it. Even the best
| screens can't show even a small fraction of the contrast
| that the eye experiences outdoors on a sunny day. And don't
| mention printed media.
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