Artificial Sunlight (official topic)

@fhr by measurement equipment, certainly, but human vision is far from a scientifically calibrated photometer.

The optical illusion I showed is one example. It's like human hearing in a way. Volume increases on a logarithmic scale (measured in phons). 

Vanta black wouldn't be much good if we truly perceived 95% gray as black, for example. As I recall the manufacturer has shown some demos but the problem with those is that we're relying on the sensitivity of the video equipment which is good (but not that good). Researchers now claim to have made it darker still although it's potentially dangerous.

Given we can't buy it though, I guess the point is moot however.

@marcdraco my point is not we can't ever perceive the difference, my point is that behind a fresnel lense, behind a Tyndall scattering filter and next to a super bright cob led, then it would be indistinguishable. 

And you can easily buy 99+ black paint

No progress on the physical light yet, but I have made some interesting discoveries. That company Yuer Skylight that seemed to make exactly what I was after? I found their patent on the WIPO website. Link's here for anyone interested. The original document is in Chinese, and the site translator might lose a few crucial points (one day's translation said a back plate needed to be a transparent window, today it was a reflective mirror). So if anyone's comfortable with Chinese and wants to take a look, be my guest. But here's a basic schematic of their window and my understanding of how it works.

LEDs on the side (7) shine into what they're calling a Rayleigh Plate (4). From their tiktoks, this seems like a piece of plexiglass colored very light blue-- the same color as those inkjet films. The light can either travel out through the front, or into an air cavity in the back (11) before hitting a reflective panel (9) and bouncing back. The buffer panel (12), back panel (8), and heat sink (6) hold everything in place. The heat sink hides the LEDs quite well and has space for a second set of LEDs (5). They shine against a diffuser (2) and give the illusion of direct sunlight hitting the sides of the window. Gotta admit, that little touch is pretty clever...

This design seems pretty similar in theory to the design I've been playing with, so perhaps some tweaks in my design are all I need. If I get somewhere new with my design I'll keep yall posted 🙂

It's a very small and unimportant thing, but I was able to find success for Tyndall scattering with a generic inkjet printer film off of Temu as well. 

Admittedly the color in the first picture is slightly exaggerated due to auto-brightness correction from the camera, the 10000 lumen lightbox in a dark room produced a pretty impressive effect. 

17 years ago, I laid down on my back and stared up at the sky in the middle of a courtyard of a 100 year old building, and realized that, from where I was laying, even if the sky were somehow fake, from nowhere in the courtyard, would I have been able to see any edges to prove it as such.

As a matter of intellectual honesty, I had to, in that moment, admit that I couldn't reasonably demonstrate that I was actually outdoors, and not in say, some elaborate spaceship or bunker or something akin to that. 

From there, it sparked in me one of my biggest dreams has been the creation of an artificial sky inside of a building, a dream which has grown with age, not diminished, given my rapidly declining health and intolerance for the heat and weather of the outdoors.

All the other particulars-- a sky that is seemingly infinite, light with parallel rays, no points of reference to dispel the illusion, all are pretty easy, but the blue? The blue was beyond me for a very long time. First time I've been able to achieve this, and it's pretty exciting. 

Just figured I'd share this, as a little "hey, there's cool stuff!"

Would photographer umbrella be a decent alternative to a parabolic dish? Judging from the image, it's not a proper shape so even determining "focal point" would not be obvious. 3 observations:

* It seems to provide some utility as it's widely used in relatively light quality-sensitive scenarios

* It can be perhaps significantly larger, maybe even allowing multiple LEDs positioned with lower wattage and perhaps better W/$ than 500W.

* I'm in a small rented apartment and need optionality/portability and this is foldable. Plus I can't easily find cheap large dish in my country for some reason.

Could this fall into category "good enough"? Or would it be completely unsuitable for reason I'm not seeing?