Laser growing up

[Markg]

I know this is an old thread but I have a Radiator and while it has some very cool color mod effects, I am hoping we can get a "old school" Laserium style color mod implementation. As has been mentioned up thread, the Laserium system had four beams bouncing off a mirror on a galvo that got sent to the four scanner pairs. Moving that mirror caused the beams to move from scanner pair to scanner pair, hence color mod when driven with a signal. A DC input was also sent to the same mirror and that was the beam torquer. One of the missing elements of modern color mod is that there were periods of no color on some or all of the scanners. There was black at both ends of the sweep. By manipulating the color mod frequency along with a healthy amount of manual gyrating of the beam torquer, we got an effect we called "hole flow". Cool swaths of holes in the pattern were possible. I am not sure who coined the term hole flow, but it wasn't me. I haven't been able to duplicate the effect on the Radiator.

[laserist]

On Greg's CYGN-B thread he developed a ILDA color mod circuit that emulates Laserium's technique. It's worth a look. I bought a Radiator and played with it a bit. It has a bunch of nice features. The color mod paradigm has some nice looks, but the paradigm was so far from the old laserium technique that a question about color mod gain just resulted in confusion. The thing that Laserium had that's been lost in general was that it was all about the ability to perform in real time. You could respond to a guitarist bending a string - in real time. Mostly today it's about really nice complex images with a pretty static color mod doing their thing more or less to the tempo of the music. It does kind of kill me when the music doesn't change but the image does, but that's me. There must be exceptions, but I'm not tuned in enough to have seen them..

[Greg]

Credit where due, laserist described the theory of operation of the RYGB to RGB colormod board. I took on the implementation. In any case, it would have been expensive to expand this to a four channel system, and like most but not all things, and especially not analog image generators, the function can easily disappear out of physical form into software.

I may be stating the obvious to those reading, but the key to the whole colormod on RGB thing is to secure, either through API or one's own code, the HSV to RGB function. With this function, chopper is Value, colormod is Hue*, and Saturation is a third modulation signal input that didn't exist in the Laserium system. There is so much to explore in my current system that I haven't got around to using image oscillator input and AM effects with colormod and saturationmod yet.

* A simple algorithm is needed to threshold the Hue values for the Laserium colormod effect.

Hole flow like majority charge carriers in P type semiconductor, that sounds authentic. The attached photo is particularly germane, pun intended, for is this perhaps a specimen of the hole flow effect?

The photo is from, unsurprisingly enough, any color you like from dark side. It is really great because the image shown was generated not from XYRGB data on the tape, but from XY + a true original 48kHz 24 bit digitized colormod signal generated on a 6b in the hands of a master performer. That is a rare and interesting artifact. The fact that the output looks pretty much like what it is supposed to look like proves the existing colormod code is correctly simulating the original effect.

[Markg]

Not sure what semiconductor theory has to do with it, but the effect was the black "holes" in the pattern (typically a spiral) flowed throughout the pattern in a pleasing way. They typically had a sinusoidal shape on both sides of the hole because it was driven by rapidly twisting the beam torquer pot back and forth by hand.

What I am describing has nothing to do with converting HSV to RGB (unless I am missing something because that's already happening the Radiator). It is simply that at both ends of H spectrum there is black. Assuming the existing H spectrum runs from blue to red it should be black, blue to red, black. Using a voltage controlled 0-10v analogy: Existing: 0 volts = blue, 10 volts = red. Proposed: 0 volts = black, 1 volt = blue, 9 volts = red, 10 volts = black. (1 and 9 volts are arbitrary just to show progression). Thinking about driving it with a sine wave: bottom of the trough is black, peak is black, in between the color shifts.

I think this would recreate (as much as possible with single scanner laser) the Laserium style color mod.

[Markg]

I guess I should mention that I stopped doing Laserium shows in June 1980 so none of the "what is coming off the tape" stuff is relevant to me as we were still only using the basic control track from the Teac when I was doing shows. I wish I could find a picture of what hole flow really looked like, but I have yet to find one. This is me at a very early version of the console (note no outboard joysticks), likely shot in late 1974 at Morrison in San Francisco. I was the second laserist to be hired (not counting Ivan and Charlie) in July of 1974 when we were doing shows from "the pit" at Griffith and the "console" was a panel of switches and motor speed controls and the cycloid generator was in it's own box. We used both ends of the krypton laser with 50% mirrors at both ends. One end was for the lumia effects, the other for the scanners.

[Greg]

That is a well known photo. Impressive. You have found the right discussion group. Welcome. Please would you remind me of Charlie's last name? I keep forgetting, and I don't want to forget that. Did you ever perform Starship?

May I suggest reading beginning post #91 in thread CYGN-A? The reposted photo summarizes the operation of the circuit being developed. laserist is right, you could produce Laserium colormod by switching to this circuit's RGB output and using the Radiator's XY.

Is the other attached photo the console of what you were using in your photo? Is this what a mark 4 system looked like?

[Markg]

I have looked at the CYGN-A posts you pointed to. I was really hoping Christopher (@swamidog) would just build that mode into the Radiator.

That is likely a photo of the console at the Morrison. It was the second one built - the first went to the Hayden in New York. I don't recall using any terminology to describe it like Mark 4 etc. I'm not sure if they ever replaced it or just kept adding on to it to keep adding functions. I know they did some adding to it, but it's possible it got completely replaced at some point - I just don't remember. That show opened 50 years ago at about this date. Ron (@ronhip) may remember more.

I don't even remember exactly what other shows we did at the Morrison in the original run from 1974-1980. I know we did the original Laserium 1 and likely 2. Ron and I put together the music and programming for Laserium San Francisco which was only ever done there. It featured the music from the Bay Area. I believe it came before LaserRock, but I could be wrong. If it did, it would have been the first all rock Laserium show, not LaserRock.

[Greg]

Interesting info, thanks! I don't know if updates to the Radiator are occurring at this time, but I'd be happy to share my colormod code with Christopher at any point, though it's so simple he probably has little need of it.

[Markg]

This is as close as I have been able to get using the Radiator.

[swamidog]

you can do something kind of like that with radiator. this is some pretty early experimentation i've been working on. i'm taking audio, boosting the voltage levels to +/-5 and running it into a triple bandpass filter and using the output to drive the cv inputs on radiator running a few different patches. in the first video sequence, i'm changing the LFO speed based on frequency filtered audio. that makes for some additional interesting effects. ithe video is pretty rough and it made my phone camera unhappy, but...

(watch at 1080p60)

Credit where due, laserist described the theory of operation of the RYGB to RGB colormod board. I took on the implementation. In any case, it would have been expensive to expand this to a four channel system, and like most but not all things, and especially not analog image generators, the function can easily disappear out of physical form into software.

I may be stating the obvious to those reading, but the key to the whole colormod on RGB thing is to secure, either through API or one's own code, the HSV to RGB function. With this function, chopper is Value, colormod is Hue*, and Saturation is a third modulation signal input that didn't exist in the Laserium system. There is so much to explore in my current system that I haven't got around to using image oscillator input and AM effects with colormod and saturationmod yet.

* A simple algorithm is needed to threshold the Hue values for the Laserium colormod effect.

Hole flow like majority charge carriers in P type semiconductor, that sounds authentic. The attached photo is particularly germane, pun intended, for is this perhaps a specimen of the hole flow effect?

The photo is from, unsurprisingly enough, any color you like from dark side. It is really great because the image shown was generated not from XYRGB data on the tape, but from XY + a true original 48kHz 24 bit digitized colormod signal generated on a 6b in the hands of a master performer. That is a rare and interesting artifact. The fact that the output looks pretty much like what it is supposed to look like proves the existing colormod code is correctly simulating the original effect.