What we need is sensors that can scan polarization on a per-pixel basis (like 256 orientations per pixel per image. Then it would be much easier to detect and remove consistently polarized components of the image (as specular reflections from glass are).
This would just be a fully electronic/computational version of a mechanical polarizing filter.
You only need 4 parameters to describe the polarization at a single wavelength[1]. Naively this could be 4 parameters per color channel, so 12 channels overall. I think you could potentially need more color channels though to capture the full spectrum. But 12 channels at least looks feasible for a camera.
On second thought for dealing with reflections you might get away not capturing the "V" Stokes parameter, as you might not care about circular polarization.
edit2:
The I,Q and U parameters can be captured fully by a single polarization filter at three different rotations. This could be feasible with existing cameras with a tripod and a static subject. I wonder if this has been done before.
You can buy [1] polarization cameras, both mono and with a Bayer filter. They're expensive right now, but I agree it would be really cool to see what could be done with a consumer grade version in a smart phone.
I'm pretty sure he means a single byte-valued parameter. As you mention a single parameter is not enough to fully describe the polarization but maybe it's good enough - I guess you would average across colors, and say circular polarization would lead to a basically random value.
Due to quantum physics, there's actually only two degrees of freedom in the ways light can be polarized, referred to as the "Jones Vector". In other words, it's impossible even in theory to distinguish between light that has exactly two perpendicular polarizations mixed together and light that is fully unpolarized and has thousands located all around the circle. That makes it surprisingly possible to build a camera that captures _everything_ there is to know about light at some particular frequency.
Not quite — that’s for polarized light. For general light that may be unpolarized, you need four parameters. You can use the Stokes parameters, or, if you’re feeling very quantum, you can describe the full polarization state of a photon by a 2x2 density matrix. (I have never personally calculated this, but I’m pretty sure you can straightforwardly translate one formulation to the other — the density matrix captures the polarization distribution of a photon sampled, by whatever means, from any source of incoming light.)
> [...] remove consistently polarized components of the image (as specular reflections from glass are).
It was my understanding that reflections in glass can be either polarized or non-polarized, or a mix of both.
If you use a polarizing filter on a camera (e.g. when taking photos of artwork through glass, or shooting over water that you want to see into), you will often find that it does not remove all reflections.
Yes, because my mom* is not going to carry that around to take pics of the grandkids.
Just because something exists does not mean it is practical. I can totally see how having a software solution that Apple can include in its fakeypics app, then my mom would be able to take advantage of this.
planede|1 year ago
You only need 4 parameters to describe the polarization at a single wavelength[1]. Naively this could be 4 parameters per color channel, so 12 channels overall. I think you could potentially need more color channels though to capture the full spectrum. But 12 channels at least looks feasible for a camera.
[1] https://en.wikipedia.org/wiki/Stokes_parameters
edit:
On second thought for dealing with reflections you might get away not capturing the "V" Stokes parameter, as you might not care about circular polarization.
edit2:
The I,Q and U parameters can be captured fully by a single polarization filter at three different rotations. This could be feasible with existing cameras with a tripod and a static subject. I wonder if this has been done before.
cornellwright|1 year ago
[1] https://thinklucid.com/product/phoenix-5-0-mp-polarized-mode... (among many others)
im3w1l|1 year ago
HALtheWise|1 year ago
https://en.wikipedia.org/wiki/Jones_calculus
amluto|1 year ago
johnmaguire|1 year ago
It was my understanding that reflections in glass can be either polarized or non-polarized, or a mix of both.
If you use a polarizing filter on a camera (e.g. when taking photos of artwork through glass, or shooting over water that you want to see into), you will often find that it does not remove all reflections.
https://en.wikipedia.org/wiki/Brewster%27s_angle
buildbot|1 year ago
https://thinklucid.com/polarized-camera-resource-center/
dylan604|1 year ago
Just because something exists does not mean it is practical. I can totally see how having a software solution that Apple can include in its fakeypics app, then my mom would be able to take advantage of this.
*Avoiding the use of the phrase "your mom"!
ikari_pl|1 year ago
very interesting device, also took about 8 angles of every photo and built a spatial interpretation, not too advanced