#diffraction grating

[talos-stims]

indium, an extremely soft metal named after the deep indigo emissions it produces | source

[nydialilian]

holo eclipse with diffraction grating! 🌈🌙☀️💥✨

I decided to sacrifice an old camera for the eclipse and see and capture everything through the camera screen. I guess the clouds in Monterrey acted as a filter, preventing my sensor from burning out 🙈 lol

[andmaybegayer]

I haven't been wearing my diffraction grating for about a year now because with the pandemic I haven't really been going anywhere with lights I didn't already know the spectrum of, but I was watching the new Philosophy Tube entry on Transhumanism and it reminded me how much I enjoyed having it on.

It's back on and it feels so good, I love secret little ways of perceiving the world, as you can probably tell from my photographic habits. These glasses have different dimensions than my old ones and my reflexes are a little rusty so I still have to do some tricks to locate the appropriate spectra but it's coming back fast. I'm also experimenting with a shorter length of grating to see how much I really need. I'll be back up to speed in no time.

[bonesandpoemsandflowers]

[nydialilian]

Ongoing project: Holonights Diffraction grating + cinestill 800t 🌈✨🌙🚦🌃🎞️

[andmaybegayer]

hey i just started doing the diffraction grating thing, any advice on interpreting the new visual info? so far i can tell a smooth spectrum from a broken spectrum from separate light sources and thats abt it

[This is what the refrance]

Two categories here:

Pairing source and spectrum

The simplest trick here is that the blue end will point towards the source because blue light is diffracted least and red most. If you draw an imaginary line from the red end through the blue end and extend it out, it'll hit the source. You can also combine this with a small head-tilt, which will give you two imaginary lines that intersect at the source.

At first this will be very time consuming to path out, but you'll gradually internalize how the spectra move at varying distances and it'll become pretty quick, a lot of this is just about wearing it out and training your brain passively. I had a bit of a time driving with this in the first two or three days but it was completely fine thereafter.

For bigger sources the spectrum will also just look like the thing itself, so you can just go on shape.

Identifying lights

Easiest start here is just looking at some lights you know. Orange sodium vapour street lights, LED lights in your house, fluorescent bars in offices, etc. You'll learn their spectra pretty quickly, and if you see one you aren't sure about searching for "X spectrum" online will usually turn up graphs like below.

LED's are now most common and are easy to spot by the huge drop around cyan-ish blue:

Orange high-pressue sodium vapour is really easy to see on the road, and it's easily identifiable because it has a massive gap between yellow and orange.

In general you won't see absorption lines in things like sunlight, they're just too small and your eyes aren't high resolving enough.

If something looks really spiky and has a few very distinct lines, it's probably a gas emission like xenon or neon, or a metal halide. You can tell real neon signs apart from fluorescents and LED's cosplaying as neons by looking for very, very sharp edges to the spectrum. Phosphors in fluorescents and LED's have smoother rolloff.

Complete spectra with no holes are either the sun or incandescents or a handful of exotic specialist lighting solutions. A good place to look for exotic lighting solutions is big sports stadiums, which may have carbon arc lamps or interesting vapour lamps. If you're ever at the Smithsonian Air and Space Museum or EPCOT, look at the overhead lighting, some of it is 3M light tubes fed from three extremely bright sulphur microwave plasma lamps, which almost perfectly imitate the visual spectrum of natural sunlight.

Three very distinct red, green and blue spectra means RGB lighting, either directly or because you're looking at a modern computer screen. Older screens may still be fluorescent illuminated, in which case you'll see five or six phosphor colours like this.

That's also what fluorescent tubes and CFL bulbs will do.

Unless you work in a lab you'll probably only see a small variety of lights, and you'll quickly become familiar with them. If you see a light you don't recognize it's still worth remembering some interesting features so you can identify it if it comes up again.

[andmaybegayer]

I moved my diffraction grating over to my left eye so that it would stop getting in the way when I use a camera eyepiece, and it is really really weird. I thought it would be a couple hours before I had switched the brainwiring over and could match sources to spectra again but it's been two weeks and its still not anywhere near as quick as it used to be. Ocular dominance is a helluva thing.

At the moment I have a decent pair of heuristics for getting it to work but those can only operate so quickly, and they're next to useless for large clusters of lights stacked up close to each other, like oncoming car headlights.

[andmaybegayer]

Decided to take off my diffraction grating because I’m not going anywhere where I could see new mysterious new light sources and it mostly just gets in the way of cleaning my glasses properly as of late.

My brain has wired in tracking lights with the grating hard enough that I keep instinctively trying to pick up emission spectra for bright objects and the lack of feedback makes me go through almost a quarter turn before I catch myself. Fortunately the lines come in at the same depth of focus as the light in question so I doubt it’s putting any undue strain on my eyes.

I do want to go get a near-UV laser pointer for getting emission spectra off common objects but probably gonna have to wait until shipping and post get back to normal.

Here’s a photo I took through it a while back showing how a setting sun has more or less the full spectrum, but with all the blue stripped out because it’s all going to become daylight closer to the horizon. (the thin spectrum on the right just below the horizon is the one that matches the sun)