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What's the physical basis for this effect? Does it happen in reality or is it a style choice?

by hughes 4mo ago

tobr 4mo ago
Came to ask this. I suppose if the edge of the sun glows in a different color than the rest, it would tint the edge of the shadow too? So maybe appropriate for sunsets, where the sky near the sun is red but the sun itself still glows bright white. Honestly just guessing.
adamjs 4mo ago
This seems more like a chromatic aberration "hack" for HDR landscapes (intensely-lit portions of the scene would have color fringing apparent at the boundaries of light/dark due to dispersion in the observer's lens). (And it's def a style choice, looks cool when done right! :)) https://en.wikipedia.org/wiki/Chromatic_aberration https://en.wikipedia.org/wiki/Chromatic_aberration
alnwlsn 4mo ago
Not sure it happens with the sun, but if you have differently located light sources of different colors you can get shadows of different colors (because the shadow area is one source being blocked but it is still illuminated by the other sources)
- rafabulsing 4mo ago
  I had a phone that produced this effect with its torch: https://twitter.com/rmbalt/status/1200397150003302403?s=20 https://twitter.com/rmbalt/status/1200397150003302403?s=20
Dave_Rosenthal 4mo ago
Simple answer: There is no physical basis, it's style Pedantic answer: Unless the light source has different colors on different sides Complex answer: Kind of. Even a linear color fade (from reality) can turn non-linear (and therefore induce color effects) when pushed through a color grading pipeline. So if you count e.g. film emulation as a "physical effect", then yes.
- dylan604 4mo ago
  > when pushed through a color grading pipeline. So if you count e.g. film emulation as a "physical effect", then yes. I've seen some footage from a particular Red camera body that introduced some very interesting effects. This particular camera had an issue with the Green channel. The camera was used in a commercial shoot for some fast food chain's shakes. The whip cream would turn magenta when the exposure was pushed because the green channel just wouldn't get there as fast as the red and blue channels. The secondaries had to go dig out extra green channel data plus other tricks to get the whip cream to end up white. After pushing other footage, the magenta tint could be seen else where as well. TL;DR it's not just film emulsion issues where weird edge case things like this happen.
  - dgently7 4mo ago
    wasnt that magenta highlights thing a pretty well known deficiency of the reds for a long time? (unsure if they resolved it in recent ones)
    - dylan604 4mo ago
      Not sure. I never had to work with Red footage to that extent. I just remember the colorist showing it to me. Maybe he knew about it and just pointed it out to me because it was such an extreme example. I wasn't a colorist, just someone that worked with a colorist. An assistant would even be glorifying it.
soraki_soladead 4mo ago
The post links another that goes into the theory a little: https://shahriyarshahrabi.medium.com/in-the-valley-of-gods-style-saturated-shadows-in-blender-lightbake-791113deeba5 https://shahriyarshahrabi.medium.com/in-the-valley-of-gods-s... Apparently a combination of Mie and Rayleigh scattering. - https://en.wikipedia.org/wiki/Mie_scattering https://en.wikipedia.org/wiki/Mie_scattering - https://en.wikipedia.org/wiki/Rayleigh_scattering https://en.wikipedia.org/wiki/Rayleigh_scattering
- skupig 4mo ago
  I think the effect the author is talking about is definitely caused by atmospheric scattering, but the painted effects are different. Those are more likely inspired by overexposure, aberration, HDR, etc. Makoto Shinkai specifically is a filmmaker and often emulates camera effects like lens flare.
AlotOfReading 4mo ago
It happens in reality, though I've only noticed it with desert sunlight. It's caused by light cast into the penumbra from scattering and diffuse reflection. You can't see this in the lit area because your photoreceptors saturate, which looks white.

What's the physical basis for this effect? Does it happen in reality or is it a style choice?

by hughes 4mo ago

What's the physical basis for this effect? Does it happen in reality or is it a style choice?

tobr 4mo ago

Came to ask this. I suppose if the edge of the sun glows in a different color than the rest, it would tint the edge of the shadow too? So maybe appropriate for sunsets, where the sky near the sun is red but the sun itself still glows bright white. Honestly just guessing.

adamjs 4mo ago

This seems more like a chromatic aberration "hack" for HDR landscapes (intensely-lit portions of the scene would have color fringing apparent at the boundaries of light/dark due to dispersion in the observer's lens). (And it's def a style choice, looks cool when done right! :)) https://en.wikipedia.org/wiki/Chromatic_aberration https://en.wikipedia.org/wiki/Chromatic_aberration

alnwlsn 4mo ago

Not sure it happens with the sun, but if you have differently located light sources of different colors you can get shadows of different colors (because the shadow area is one source being blocked but it is still illuminated by the other sources)

rafabulsing 4mo ago
I had a phone that produced this effect with its torch: https://twitter.com/rmbalt/status/1200397150003302403?s=20 https://twitter.com/rmbalt/status/1200397150003302403?s=20

Dave_Rosenthal 4mo ago

Simple answer: There is no physical basis, it's style Pedantic answer: Unless the light source has different colors on different sides Complex answer: Kind of. Even a linear color fade (from reality) can turn non-linear (and therefore induce color effects) when pushed through a color grading pipeline. So if you count e.g. film emulation as a "physical effect", then yes.

dylan604 4mo ago
> when pushed through a color grading pipeline. So if you count e.g. film emulation as a "physical effect", then yes. I've seen some footage from a particular Red camera body that introduced some very interesting effects. This particular camera had an issue with the Green channel. The camera was used in a commercial shoot for some fast food chain's shakes. The whip cream would turn magenta when the exposure was pushed because the green channel just wouldn't get there as fast as the red and blue channels. The secondaries had to go dig out extra green channel data plus other tricks to get the whip cream to end up white. After pushing other footage, the magenta tint could be seen else where as well. TL;DR it's not just film emulsion issues where weird edge case things like this happen.
- dgently7 4mo ago
  wasnt that magenta highlights thing a pretty well known deficiency of the reds for a long time? (unsure if they resolved it in recent ones)
  - dylan604 4mo ago
    Not sure. I never had to work with Red footage to that extent. I just remember the colorist showing it to me. Maybe he knew about it and just pointed it out to me because it was such an extreme example. I wasn't a colorist, just someone that worked with a colorist. An assistant would even be glorifying it.

soraki_soladead 4mo ago

The post links another that goes into the theory a little: https://shahriyarshahrabi.medium.com/in-the-valley-of-gods-style-saturated-shadows-in-blender-lightbake-791113deeba5 https://shahriyarshahrabi.medium.com/in-the-valley-of-gods-s... Apparently a combination of Mie and Rayleigh scattering. - https://en.wikipedia.org/wiki/Mie_scattering https://en.wikipedia.org/wiki/Mie_scattering - https://en.wikipedia.org/wiki/Rayleigh_scattering https://en.wikipedia.org/wiki/Rayleigh_scattering

skupig 4mo ago
I think the effect the author is talking about is definitely caused by atmospheric scattering, but the painted effects are different. Those are more likely inspired by overexposure, aberration, HDR, etc. Makoto Shinkai specifically is a filmmaker and often emulates camera effects like lens flare.

AlotOfReading 4mo ago

It happens in reality, though I've only noticed it with desert sunlight. It's caused by light cast into the penumbra from scattering and diffuse reflection. You can't see this in the lit area because your photoreceptors saturate, which looks white.