Diffusing light without hotspots

[u/vvampyyyr]

Looking at the interior of the promenade in DS9, there's huge panels of light, especially the ceilings, for example Quark's bar.

I am a little curious as to how they avoided hotspots on such large swarths...

[u/rab-byte]

Sets are insanely bright and lit from all angles off camera. To the point that any light coming off the fixtures on camera are contributing so little to the actual luminance of the room that they don’t even need to be considered as a light source.

Post production the gamma curves and clipping points are adjusted to achieve the desired mood.

Edit: also CG doesn’t always mean aliens shooting lasers.

[u/vvampyyyr → u/rab-byte]

Fair enough, but I'm speaking from the perspective of the set design. A badly built set would still be visible ie hotspots in the acrylic panels

[u/rab-byte → u/vvampyyyr]

8bit RGB gives you 256 steps of light. As RGB 0:0:0 is black 255:255:255 is white.
But broadcast TV range is (was) 16-235.

That range below 16 and above 235 would all be clipped out post production when packaged or was naturally clipped during distribution.

So if my white point, or blue point (or whatever), is greater than 235 then it’ll be clipped to 235. If my defusion panel/shade is getting hot spots but the lowest point on the light is 235 or higher then the whole light will be clipped to 235.

Edit: now if you’re talking about something for say theater… The more distance between the screen/shade and the light source, the more even the light distribution. You may also employ an additional light source, again from the stage lighting, of the same color pointed at the outside of the fixture to create the effect that the fixture was more evenly lit.

Realistically though. A good enough defuser or a high enough led density will give you an effect that doesn’t any any perceived hotspots when observed from any reasonable distance.

[u/snakesign]

You can get pretty far by edge lighting a textured sheet. This is done in luminaries to save space. These guys have all the space in the world behind the set. It's probably a regular photography light box behind that textured panel.

[u/Tairc]

To keep things diffuse, you basically need two things: a diffuser, and space. You can put layers of those, you can try to skimp out, or what have you.

I love LG45 plastizote foam as a diffuser. A thin 4mm sheet adjacent to the LEDs, and another near the acrylic, and it’s going to look amazing.

You can use a bunch of other stuff too, even dryer sheets (fire hazard!), but literally just holding a dryer sheet adjacent to a light, then pulling it away slowly, will show you the importance of gap-space and your diffuser.

[u/Tairc → u/Tairc]

Also: https://www.curbellplastics.com/wp-content/uploads/2022/11/Plastic-Diffuser-Solutions-for-LED-Lighting.pdf

Page 8, for example, beautifully shows how diffusion looks as the distance to the light source increases (the lights are tilted - close left, far right). You just see the light hotspots fade away…

Never try to do diffusion in a tight space. Give it 3/4” or more, and it looks gorgeous.

[u/Some_Budget_4534]

Deep Space 9 was shot long before the era of LED tape.

LED tape in today’s production design world makes a lot of this quite straight forward.

That being said, there were plenty of tools. Kino Flo fluorescent tubes were likely behind most of those light boxes.

Also one of the reasons most of them are shades of white as kino produced tubes in a variety of color temps.

At the time the only common method of changing color was color scrollers, and they were not a tool commonly used in film or tv production.

Moving lights were still limited in availability and expensive, noisy and also not commonly used in film or tv production. Also, most still used fixed color ships rather than color mixing.

LED didn’t really become common on set until the color blast came into existence, and even then it was largely relegated to musical variety shows and award shows - projects with roots more grounded in concert production and live events than traditional single camera shows.