We have done 7 years of research on this and just recently brought "Virtual Sun" to the market.
If you want to replicate a window, there is more than just lumens, CCT, and CRI. In order for your brain to really believe something is a window or a skylight, you also need:
1. Separate sun and sky light components. The real sun is very directional, by the time it reaches the earth the rays of sunlight diverge by only 0.5 degrees, have a much lower CCT than the sky, and a much brighter lux profile than the rays of light from the sky. Innerscene Model A7 outputs a rectangular sunbeam the diverges at less than 2 degrees and has a CCT of 4500K and is over 2500 lux at head level when sitting under it. Compared that with Coelux which has a 10 degree divergence angle. A7's sky changes from 3000K up to well over 10000K.
2. The illusion of infinite space behind the fixture. The LEAD building standard requires all rooms to have eye level sight lines to the outdoors. Psychologically a room with windows is much more comfortable to work in than those lit only by artificial light, part of this is that most people have some level of claustrophobia - ranging from very mild (but noticeable) to panic attack inducing. Being able to see outside elevates a lot of that. We invented a new 3d display technology that allows users to see a sun at infinity, rather than something painting on the surface so it looks like a portal, not a TV or flat surface. This turns out to be an extremely hard problem, and I haven't seen anyone else do it - even coelux's sun only appears to be about 20 feet away from you.
3. Variability in CCT and intensity. Artificial light is too static which creates monotony, we are used to a variety of light profiles from natural light because of the earths rotation and atmospheric effects. When the sun is obscured by clouds temporarily, the light in the room changes slowly but very significantly - there is more diffuse light and less directional light, the CCT gets warmer, and brightness in the room may go up or down depending on the cloud thickness. Similar the CCT of light the sky changes throughout the day because of the earths orbit and how much light goes through the atmosphere at different angles. Innerscene is able to replicate this and it makes a room feel "alive" and connected to the outdoors, combined with the 3D effect it is comfortable to work/live in a space with no real windows for long periods of time.
You can't comfortably work in a room where there is strong glare shinning in your eyes, which you would get if you buy random high powered LEDs and stuck them on your ceiling. From a perfectly diffusive light object like the sky there is no glare, but you will have glare from an unshielded light fixture unless it is well diffused or you have baffles that block the light which isn't going down. Getting the directional profile of light is very important in this respect. Because our sun is always at a high angle (30 degrees) it doesn't shine into your eyes directly and the sky portion of the fixture is perfectly diffused like the real sky.
Check out our product, it's a far-cry from the $400 you mentioned but many times less expensive and thinner than coelux.
Check out a video here:
https://www.youtube.com/watch?v=XVV_-aB1jpg&t=57s
Some comparisons with Coelux: https://bit.ly/2YszzsO
We have done 7 years of research on this and just recently brought "Virtual Sun" to the market.
If you want to replicate a window, there is more than just lumens, CCT, and CRI. In order for your brain to really believe something is a window or a skylight, you also need:
1. Separate sun and sky light components. The real sun is very directional, by the time it reaches the earth the rays of sunlight diverge by only 0.5 degrees, have a much lower CCT than the sky, and a much brighter lux profile than the rays of light from the sky. Innerscene Model A7 outputs a rectangular sunbeam the diverges at less than 2 degrees and has a CCT of 4500K and is over 2500 lux at head level when sitting under it. Compared that with Coelux which has a 10 degree divergence angle. A7's sky changes from 3000K up to well over 10000K.
2. The illusion of infinite space behind the fixture. The LEAD building standard requires all rooms to have eye level sight lines to the outdoors. Psychologically a room with windows is much more comfortable to work in than those lit only by artificial light, part of this is that most people have some level of claustrophobia - ranging from very mild (but noticeable) to panic attack inducing. Being able to see outside elevates a lot of that. We invented a new 3d display technology that allows users to see a sun at infinity, rather than something painting on the surface so it looks like a portal, not a TV or flat surface. This turns out to be an extremely hard problem, and I haven't seen anyone else do it - even coelux's sun only appears to be about 20 feet away from you.
3. Variability in CCT and intensity. Artificial light is too static which creates monotony, we are used to a variety of light profiles from natural light because of the earths rotation and atmospheric effects. When the sun is obscured by clouds temporarily, the light in the room changes slowly but very significantly - there is more diffuse light and less directional light, the CCT gets warmer, and brightness in the room may go up or down depending on the cloud thickness. Similar the CCT of light the sky changes throughout the day because of the earths orbit and how much light goes through the atmosphere at different angles. Innerscene is able to replicate this and it makes a room feel "alive" and connected to the outdoors, combined with the 3D effect it is comfortable to work/live in a space with no real windows for long periods of time.
You can't comfortably work in a room where there is strong glare shinning in your eyes, which you would get if you buy random high powered LEDs and stuck them on your ceiling. From a perfectly diffusive light object like the sky there is no glare, but you will have glare from an unshielded light fixture unless it is well diffused or you have baffles that block the light which isn't going down. Getting the directional profile of light is very important in this respect. Because our sun is always at a high angle (30 degrees) it doesn't shine into your eyes directly and the sky portion of the fixture is perfectly diffused like the real sky.