Scan angle limit recommendations for different show types?

My recent experience with "user-induced scanner blowout" now has me wondering about the max scan angles we might want to use for different show types (typical graphics vs. raster vs. beams) to help protect the typical 30-40K scanner sets (DT, ScanPro, etc.) most of us are using. I think as some of us move away from the small, close controlled environments of our living room or garage shows to things a bit bigger, we need to be able to use something other than "Squeal" of the scanners to let us know when we might be getting ready to release the magic smoke...:eek:

So, for those who have worked with different scanners over the years - and keeping in mind that most of us probably can't afford a good Cambridge set and aren't running "wide-angle" scanners -

Any recommendations on max scan angles for typical graphics shows (think the Mike Dunn variety), rasters (Pangolin "Linea") and beams (i.e. SELEM!!) ?

Curious myself what the size in pangolin LD2000 relates to, IE 100 full size equals what scan angle 35 equals what scan angle?

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Originally Posted by polishedball

Curious myself what the size in pangolin LD2000 relates to, IE 100 full size equals what scan angle 35 equals what scan angle?

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Now that you mention it - me too!!

This will be a good thread to follow. After I saw your original post I deleted all rasters out of my FB3 box lol.
Scarred the shit out me.

When the music blaring you can hear the "squeal" But I'm sure I be the first to visually notice it after.

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Originally Posted by polishedball

Curious myself what the size in pangolin LD2000 relates to, IE 100 full size equals what scan angle 35 equals what scan angle?

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When I look at that slider, I see it as a percentage. 100% means the maximum voltage on the +X/-X and +Y/-Y lines. And 35 just means it's 35% of the max output. How it relates to scan angle depends on gain pot setting on the amp. You can have Pangolin set to output 100% and only get a 1 degree scan angle if the gain pot on the amp is set to nearly 0. I typically set the gain pot on the amp to max and adjust the image size in Pangolin according to what I believe is safe for the scanners. And, different shows can contain more complex images which require me to turn this down a bit in Pangolin. Most beam shows I can get away with setting Pangolin to 100%, some of them, I'll set to 100% and turn down the scan speed to around 22K if I know the beam show has complex images that might heavily tax the scanners at 30K full size.

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Originally Posted by Mattatya

This will be a good thread to follow. After I saw your original post I deleted all rasters out of my FB3 box lol.
Scarred the shit out me.

When the music blaring you can hear the "squeal" But I'm sure I be the first to visually notice it after.

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I'm pretty sure my raster-induced meltdown was my own exuberant fault -
I definitely should have reduced the zone (scan limit) size when I decided to run rasters...:o

Thanks for the info DZ, further searching I found this for figuring it out with some knowns.

http://www.pangolin.com/userhelp/scanangles.htm

John

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Originally Posted by DZ

When I look at that slider, I see it as a percentage. 100% means the maximum voltage on the +X/-X and +Y/-Y lines. And 35 just means it's 35% of the max output. How it relates to scan angle depends on gain pot setting on the amp. You can have Pangolin set to output 100% and only get a 1 degree scan angle if the gain pot on the amp is set to nearly 0. I typically set the gain pot on the amp to max and adjust the image size in Pangolin according to what I believe is safe for the scanners. And, different shows can contain more complex images which require me to turn this down a bit in Pangolin. Most beam shows I can get away with setting Pangolin to 100%, some of them, I'll set to 100% and turn down the scan speed to around 22K if I know the beam show has complex images that might heavily tax the scanners at 30K full size.

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DZ -
Do you generally set the projector settings to 100, then adjust "scan angle" with the zone settings, or use some other combination of adjustments?

What is your criteria for deciding if a scan angle / scan speed combination is "safe" for the scanners?

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Originally Posted by polishedball

Thanks for the info DZ, further searching I found this for figuring it out with some knowns.

http://www.pangolin.com/userhelp/scanangles.htm

John

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Search around the forums for "Scan Angle Calc" for a freeware applet that does the same thing:)

I still need to figure out the "safe" limits, however!!!

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Originally Posted by Stuka

DZ -
Do you generally set the projector settings to 100, then adjust "scan angle" with the zone settings, or use some other combination of adjustments?

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I've not actually played with the "zones" a whole lot. I use the settings in there from time to time for geometric correction and that's about it. It seems to add a new level of complexity to the whole thing, though if I'd spend the time with it to set things right I'm sure it would end up being much easier in some way. So really the scan angle setting in the zones are pretty much default.

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What is your criteria for deciding if a scan angle / scan speed combination is "safe" for the scanners?

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It really isn't an easy thing to do, I think it's a combination of knowing what the limits of the scanners are along with looking for artifacts in the images. In my opinion, abstracts seem to beat up scanners more than anything. Do you have "Run Like Hell" from Mike Dunn? That show has a couple abstract that are very taxing. I usually turn the size setting in Pangolin down 5% for that one. Some folks seem to think that when the scanners are really loud that it's a bad thing when really I don't think it matters at all.

One of the things I like about the DT-40 scanners I use, is that the power supply seems to be right at the limit of what the scanners are capable of. If I'm displaying a pattern too big and too fast, the first thing that I see with a DT-40 set is that the switching power supply will reset before it'll blow a fuse on the amp. You end up with an errant beam for a split second, but I think that's better than having to open up the projector to replace a damn fuse, or worse.

Shouldn't a scanfail act immediately in such a case ?

I would not prefer errant beams in any case, no matter how split that second is.

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Originally Posted by -bart-

Shouldn't a scanfail act immediately in such a case ?

I would not prefer errant beams in any case, no matter how split that second is.

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I don't think you'll see too many hobbyiest-level projectors in the US equipped with scanfail right now, but I'm sure most are using beam masks to catch those stray beams - just in case!

A piece of sheet metal and industrial-strength velcro work wonders....:)

In fairness, a beam-block isn't going to stop a static beam if it's in the normal scanning area. The point is that here in the US, we don't crowd-scan, so a static beam isn't a big deal. But yeah, in Europe, a static beam is a real problem, since it could be aimed into the audience. So a scan-fail interlock is crucial in those cases.

With regard to "how much is too much", I'm with DZ on this. You watch the pattern, and if you see distortion, you back off on the scan angle a bit. I'm running the ScanPro-50's, but I have them tuned for 30K so I can get a wider angle out of them. Thus far I've not had any trouble with them, but I don't push them too hard either.

It probably would be good to have a little discussion about scan angle and projection zones at SELEM, however. *retardo

Adam

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Originally Posted by buffo

In fairness, a beam-block isn't going to stop a static beam if it's in the normal scanning area. The point is that here in the US, we don't crowd-scan, so a static beam isn't a big deal. But yeah, in Europe, a static beam is a real problem, since it could be aimed into the audience. So a scan-fail interlock is crucial in those cases.

With regard to "how much is too much", I'm with DZ on this. You watch the pattern, and if you see distortion, you back off on the scan angle a bit. I'm running the ScanPro-50's, but I have them tuned for 30K so I can get a wider angle out of them. Thus far I've not had any trouble with them, but I don't push them too hard either.

It probably would be good to have a little discussion about scan angle and projection zones at SELEM, however. *retardo

Adam

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NOT audience scanning does keep things easier, doesn't it!
(But kudos to those who SAFELY do it right!! :D)

My beam mask is more for the "unscheduled max deflection event" of the scanners. While I've never actually heard of that happening, I'm pretty sure that if it did happen, my piece of 18GA aluminum sheet would keep it safely contained. ;)

You've definitely got my vote for a scan angle / projection zone discussion!

I know my "raster" incident was a surprise - even though I didn't reduce my projection zone (stupid, stupid, stupid...), there actually wasn't any distortion - just that agonizing scream as the scanner died, and then the graphics melted.....

I hate it when that happens! :rolleyes:

The raster images, put a huge load/stress on any scanners, and your probably better off not doing raster images , with anything other than Cambridge scanners.

At one time, i bought new Medialas scanner amps, and they didnt last too long before they blew up,
since then, i buy nothing but Cambridge for reliablilty .....

jst my .02