Tails and Defects

[norty303]

I think you may be misinterpreting the scan angle used for the test pattern. This is not the ultimate scan angle you can use, just the scan angle to set up the scanners optimally.
Sure, for graphics shows you need to 'feel' what is right for the graphics you are projecting (using ears and eyes, looking for curly corners and listening for too much squealing) but for beams you can generally open them right out.

[dnar]

... and listening for too much squealing

I did a show earlier in the year, there was a LOT of squealing when I started the laser show. But, it was juts a bunch of young girls in Anime costumes going off when they saw the show...

[planters]

Don't you like how the DJ becomes a super hero for a couple of hours? All that power at your fingertips!

[buffo]

When the slider is moved from one position say 3 to 4 the tails, wherever they are seen, lengthen substantially and in exactly the same direction. When the slider is reversed from say 3 to 2 then the tails flip exactly 180 degrees and if continued to position 1 then they lengthen in this new direction.

Try reducing your scan angle to 8 degrees first, and then repeat this test. Do you still have exactly the same results? If so, then the problem can be solved by adding more anchor points at the ends (start and finish) of the blanking jumps for each frame. Not exactly sure how to do this in Beyond, but in LaserShow Designer there is a menu item called "Eliminate Blanking Jumps" that usually fixes this.

However, if you find that the tails go away when you have your scan angle down to 8 degrees, then the problem is not caused by poor frame design or the color-shift setting, but rather because you are pushing your scanners too hard.

In this case, once you get the image to look good, you can start increasing the scan angle above 8 degrees while watching for the tails to re-appear. When they do, stop. That's your maximum scan angle for that frame. If it's a typical frame in a show, then you've got a benchmark maximum scan angle for graphics shows that you shouldn't exceed.

Regarding scan angle, 8 degrees is too small to be useful to me.

As Norty said, 8 degrees is not the ultimate limit. You can scan wider than that. But for testing purposes, you want to be at 8 degrees or less, because at that angle you should be able to display any normal frame with no artifacts whatsoever. If you can't then there is something else wrong, and you need to fix that first.

What is the typical real world angle that most people scan at?

For graphics shows I usually run between 20 and 30 degrees optical. For beam shows I might pump it up to 50 degrees or so, but usually not much more than that. (Note that for beam shows, if you reduce the scan speed you can scan even wider without over-driving your scanners. Besides, beam shows often look better at slower scan rates anyway - even when you're down to 15Kpps.)

A lot of this depends on the scanners you have though. A set of PK-30's will not be able to scan nearly as wide as a set of Cambridge 6800's, for example, even though technically they are both 30K scanners.

Looking thru a couple dozen YouTube videos it seems that the typical projector is running at least at 30-40degrees.

It's very hard to estimate the scan angle by looking at a YouTube video. But most scanners should be able to handle 20 degrees at least, and 30 degrees is a reasonable angle for simpler graphics shows.

Adam

[planters]

Got it. I'll try the 8 degree set up first. From memory , while tuning the scanners the pattern looked good at that small angle.

[swamidog]

i'm sure you've done this, but duble check to make sure the beam is hitting the scanner mirrors squarely.

Got it. I'll try the 8 degree set up first. From memory , while tuning the scanners the pattern looked good at that small angle.

[norty303]

Got it. I'll try the 8 degree set up first. From memory , while tuning the scanners the pattern looked good at that small angle.

Too be honest, if you've tuned your scanners on the ILDA pattern at a big scan angle, there's a good chance you're not actually driving them hard enough at 8 degrees.

[White-Light]

Don't you like how the DJ becomes a super hero for a couple of hours? All that power at your fingertips!

Quite topical in the Uk at the moment for all the wrong reasons:

http://www.independent.co.uk/news/uk...s-8218187.html

(Excuse the quick tangent to answer the point)

[planters]

I find this tuning thing confusing. I think everyone commenting here has a general understanding of the process as Buffo describes it. However, the impact of a significant change in the scanned angle as in 8 to 30 degrees I would think needs to be a part of the original tuning sequence. The substantial increases in velocity probably will change the balance between gain and damping. And what, if as I do, the scan is made non-square and the rectangular pattern is what needs to be tuned?

[norty303]

I think the point of the ILDA test pattern is that it tunes a scan set for optimal operation across the range of patterns its likely to encounter. Yes, you can tune for a specific behaviour, but at the expense of another.

TBH, this is starting to sound reminiscent of another thread in recent history, where someone was questioning the validity of the ILDA test pattern. It got quite 'interesting' to say the least... I'll try and dig it up if I can. Maybe it was something to do with the EMS7k group buy and testing that Bill Benner did, maybe not, my memory is fuzzy right now.