4 ms·

that's fascinating, and a lot more involved than what I expected (my guess was something more like off-the-shelf color correction)

loeg 7y ago
The palette cards they carry around remind me of white-balancing.
- mstade 7y ago
  If I understand things correctly it's not entirely different to white balancing either, just that the difference between white balancing a monitor or camera is that you don't really have to correct for the scattering of light through air because it's negligible at the distances you're likely to work with. The trick here – again, if I understand correctly – is that this method also finds the light scattering/absorption characteristics and corrects for those as well. It might seem obvious, but I think it's more involving than it seems, because light scatters differently in different environments and I think – again, I might be wrong, this is just my understanding – this method accounts for that by using multiple images at different distances to gather the parameters to find the scattering and absorption characteristics. This is what makes it physically accurate and not just "make these colors mostly look good" which is really quite cool and useful!
  - kd5bjo 7y ago
    If I remember correctly, the percentage of light that passes through a column of water exponentially decays with distance, like stacking a bunch of fixed-percentage optical filters on top of each other. They’re using parallax shift between multiple images to generate a depth map, so they have a measure of the amount of water obscuring each pixel. I’m not sure how they’re finding the optical properties of the water; there’s something about using the darkest pixels in the image for calibration that I didn’t quite follow.
- planetmaker 7y ago
  It's actually exactly that. Her set of skills is to do that actually accurately with setpoints for both distance to the objects as well for different wavelengths simulataneously.

loeg 7y ago

The palette cards they carry around remind me of white-balancing.

mstade 7y ago
If I understand things correctly it's not entirely different to white balancing either, just that the difference between white balancing a monitor or camera is that you don't really have to correct for the scattering of light through air because it's negligible at the distances you're likely to work with. The trick here – again, if I understand correctly – is that this method also finds the light scattering/absorption characteristics and corrects for those as well. It might seem obvious, but I think it's more involving than it seems, because light scatters differently in different environments and I think – again, I might be wrong, this is just my understanding – this method accounts for that by using multiple images at different distances to gather the parameters to find the scattering and absorption characteristics. This is what makes it physically accurate and not just "make these colors mostly look good" which is really quite cool and useful!
- kd5bjo 7y ago
  If I remember correctly, the percentage of light that passes through a column of water exponentially decays with distance, like stacking a bunch of fixed-percentage optical filters on top of each other. They’re using parallax shift between multiple images to generate a depth map, so they have a measure of the amount of water obscuring each pixel. I’m not sure how they’re finding the optical properties of the water; there’s something about using the darkest pixels in the image for calibration that I didn’t quite follow.
planetmaker 7y ago
It's actually exactly that. Her set of skills is to do that actually accurately with setpoints for both distance to the objects as well for different wavelengths simulataneously.