why slow down scan speed?

[dream]

EDIT: The way some of the members here have desperately tried to identify my location and nationality for whatever reason they believed was needed for by asking an admin to check my profile logs and researching me by the content of my posts has been very creepy and unnecessary. So bye.

[colouredmirrorball]

The slower you go the more accurate the patterns are. A circle scanned at 40k might have a gap or lines might have tails that aren't there at 24k.
Also scanning slower allows for a larger scan angle.

[swamidog]

accuracy is less relevant for beam shows. the idea is there's a relationship between beam speed and apparent brightness.

The slower you go the more accurate the patterns are. A circle scanned at 40k might have a gap or lines might have tails that aren't there at 24k.
Also scanning slower allows for a larger scan angle.

[slicklasers]

Slower scan speed means the beam is left there longer, which makes it appear brighter.

[planters]

Slower scan speed means the beam is left there longer, which makes it appear brighter.

If the circle is scanned 40 times in a second vs 30 times, I believe it would appear no brighter as long as the same laser was modulated at the same percentage, duty cycle. The limit being, continuously on. I suspect it is the duty cycle that changes if this effect is real. It would be pretty easy to check by placing an oscilloscope across the modulation leads for a given laser component and scanning a very simple pattern. You could calculate the area under the VxT.

[JohnYayas]

Increasing speed requires an increase in unlit control points so it isn't as simple as just scanning the same frame more. Also, frames aren't typically scanned 30 or 40 times. More like once. So, if the frame only has enough of a time slice to be displayed once and you increase the scan speed 1.5x times, how are you going to display that frame 1.5 times in that time space? Are you going to scan it once then just 1/2 of it? Or will you scan it twice while taking a portion of the next frame's time slice? An alternative would be to just interpolate and add more points to the frame but that would have roughly the same result as scanning slower except that there would possibly be less hot spots. Of course, this is when using a frame based approach.

If the laser software doesn't use a frame based approach then the software can just scan the frame as fast as it once and dynamically create the next frame and scan it. And so on and so on. This a really good way to do it and will result in some really smooth output. It probably will be closer in appearance to the old analog based equipment. But, it will only work for dynamically generated frames or if the frames are prerendered for a constant point rate. The advantage of this would be made really apparent when slowing down the animations to a slow motion state since each frame can be computed to fit the time no matter how much you slow it down. With a frame based approach you'd stay on the same frame for awhile and then finally jump to the next one.

Anyway, sorry to ramble but those are some various things to consider. It just isn't as simple as speeding up or slowing down the point rate.

[planters]

Yes. If a 1watt laser is on all the time ( duty cycle is 100%) then I believe the pattern will appear the same brightness no matter how fast or how many times it is overwritten. If it is on 50% of the time ( duty cycle at 50%)...the same thing.

[lightlinked]

There is also an aesthetic touch that changing the scan speed imparts. A low scan speed with beams is kind of stroby, depending on the pattern. Also brighter as mentioned before, since the dwell time is longer. It's part of the expressiveness and dynamics of the performance, hence midi mapping it to a fader or knob along with playback speed which you need to alter to keep a cue in time with music. With certain abstracts, the scan speed can really change what is projected. that flicker is part of the charm of laser. As mentioned before, with graphics, you might need to lower it to bring back sharp corners or scan accurately depending on your projector.