[HN Gopher] Why dark and light is complicated in photographs ___________________________________________________________________ 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. ___________________________________________________________________ (page generated 2022-03-13 23:00 UTC)