41–50 of 114 posts
It's just a dichroic beamsplitter, which is a standard optical element available from online sellers. Variants of these are commonly sued in scientific experiments, optical devices, etc...
Here's one for under $300: https://www.meetoptics.com/beamsplitters/plate/longpass-dich...
Just search for: "589 nm beamsplitter".
Earlier quoted context omitted.
Did you see them putting the black panels up in the video and measuring the color spectrum off the costume, and covering the skylight? They did that to get a 'perfect' mask. If you use infrared, which is generated by random environmental objects, how would you prevent random spill? Practically (my understanding) is if you got random spill on the surface, you'd get random alpha in the mask. The point of using the sodi…
Near infrared isn't generated by random environmental objects. You're thinking of far infrared. Infrared is a big spectrum, much larger than the visible spectrum. It may be generated by lights but could be filtered out. It is generated by the Sun, but so is the sodium wavelength. The technique would work indoors just as well as the sodium one, but with important advantages. I think it could even work pretty well outd…
> but with important advantages
What's the benefit over using any other single frequency visible light?
Even if the atmosphere absorbs most of a particular band, if any of it gets through, your mask is going to be messy, which kind of ruins the point; I don't know anything can really fix that for outdoor purposes?
I mean, broadly speaking, all you need is a way to emit a sharp frequency band and avoid having any environmental pollution in the same band.
If there's a good way to do that in near-IR, it would work; but I feel like the same could be said about pretty much any frequency.
I'm not aware of anything specific about near-IR that makes it particularly attractive.
(but, clearly, I'm no expert in near-IR)
Earlier quoted context omitted.
Near infrared isn't generated by random environmental objects. You're thinking of far infrared. Infrared is a big spectrum, much larger than the visible spectrum. It may be generated by lights but could be filtered out. It is generated by the Sun, but so is the sodium wavelength. The technique would work indoors just as well as the sodium one, but with important advantages. I think it could even work pretty well outd…
Huh, my bad, I thought thermal sources (ie. like random hot stuff, not glowing hot stuff) emitted a wide band of frequencies including near-IR, but fair enough. You'd still get it from any sort of incandescent light source right? (same as a sodium lamp) > but with important advantages What's the benefit over using any other single frequency visible light? Even if the atmosphere absorbs most of a particular band, if a…
> It would allow using full spectrum lighting, and would be easier to selectively filter.
Making a broad spectrum IR filter is far easier than a notch filter for a single visible wavelength. In general it's harder to make more selective filters and an IR filter can be much less selective because the IR band is so large and far away from any visible light.
Also the infrared version would allow using any color background including black, and the on set lighting would appear to the eye exactly as it does to the camera. With the sodium vapor process the bright yellow background would make everything on set look different in person because the eye wouldn't be able to subtract it the way the camera does.
Yes, you would need a filter on any incandescent light. But this is also true of the sodium vapor process. Actually I'm not sure anyone makes a sodium vapor wavelength notch filter suitable for putting in front of an incandescent light. Consequently, as seen in the video, they restricted themselves to special LED lights that emit essentially only three wavelengths. These are very much not full spectrum and will not produce natural colors for some materials. And they had to completely block all windows, whereas for IR you could just install some IR blocking film on the windows and still use natural sunlight.
tl,dr: Narrow-band lighting and optical filtering.
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His employees, (Wren especially), give off a silly fake enthusiasm vibe (or maybe he's just like that, and that's why he got hired, I don't know) but Nico only really shows up in the videos he wants to make. Guy seems like he's getting to live out his dream. The videos he spearheads are both technically impressive and time-consuming, such as Anime Rock Paper Scissors, which was a groundbreaking use of AI diffusion models a year ago, or this one.
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Near-infrared penetrates very well. The same intensity is much safer, up till you get to the levels of radiation that are dangerous regardless of how they're distributed in your tissues. That's one of the things that makes it suitable for thermal nano cancer therapies. You (1) Create a nanoparticle with a gold core of the right size that it excites when exposed to near-infrared radiation (the far end of "near" is ide…
>Near-infrared penetrates very well. The same intensity is much safer Glowing-hot steel produces enough IR that the workers that work with it have 7 times the rate of cataracts as the general population.
NIR is much safer than the visible spectrum at the same power levels. The threshold for a few minutes of high-intensity NIR increasing your chance of eventual cataracts is staring at an NIR source 10x brighter (w/cm^-1) than the sun integrated across all its wavelengths. The threshold for sun-colored wavelengths causing eventual cataracts above the baseline from a few minutes of staring is under 1x.
Also worth noting, very very near IR (basically red, though we can't see it) doesn't quite enjoy those same properties, and during their time working with hot metal you'd expect a lot of energy in that band.
Also worth noting, many steel workers are exposed to dangerous amounts of visible light too. I absolutely believe that they can get enough NIR to cause problems, but if I wanted to try to prove that NIR specifically causes their problems to somebody else then I'd want to try to account for that fact (and for incidental welder exposure, ...).
Hmm, why don't people do this with near infrared? It would allow using full spectrum lighting, and would be easier to selectively filter. I'm guessing the answer is "they do, it's just uncommon and you haven't heard about it"
Does the magic color need to be within the frequency range that the camera and video format can record?
Building 2 nigh identical cameras, but one with a sensor outside of the frequency range of the other, is probably a very expensive custom job.
Very interesting stuff. I'm curious if this means anything in terms of good vs perfect technology or what tech wins out in practice. This process seems just plain better than green-screen, so why did it lose out? Is is just that green screen is good enough? Was it too hard to do this sodium vapor process with random cameras back in the day? Are sodium vapor lights bad enough in some way that practically it lost out?
This was addressed at the end of the video: The main points are that it can't be used outside, or when the shot includes the subjects' legs/feet (as the ground would need to be an amber-screen as well), and on top of that, it requires a certain level of setup which some shoots can't afford.
The original beamsplitter cube isn't some exotic custom device that would cost tens of thousands to make. It's just a dichroic beamsplitter, which is a standard optical element available from online sellers. Variants of these are commonly sued in scientific experiments, optical devices, etc... Here's one for under $300: https://www.meetoptics.com/beamsplitters/plate/longpass-dich... Just search for: "589 nm beamsplit…
However, I'd guess these are the components the guys are using between the prism and the cameras.