Scanner Help

[ljk]

I picked up a pair of Cambridge 6800HP scanners and CB6580 rev D drivers. When I hook them up to my QM32 card with the ILDA test pattern it looks good at 5K but I seem to get a lot of flickering. So I turn the scan speed up from 5K and the image starts to distort even to the point of not resembling the test pattern "even before I get to 30K". Would this tell me that the scanners were adjusted for 5K?

If so would it be normal that the image looks distorted at higher scan rates?

Any tips would be a great help. Not really sure what I do next. But I know I did not want to make changes to the pots if not needed.

Thanks in advance

[allthatwhichis]

Post a few pictures and someone more familliar with those scanners might be able to point you in the right direction.

[chad]

how big are you trying to scan the image?

Remember the ilda tuning speed is based on scan angle.

chad

[buffo]

Aaron, did you have someone particular in mind?

He's got a copy of the tutorial, and he might try some tuning later.

Chad is correct: need to determine the scan angle first. If the angle is 8 degrees or less and the image still looks lousy at anything above 5K, then he's going to have to re-tune them. On the other hand, if he's scanning at some insanely wide angle (say, 50 degrees), then just lowering the angle back to 8 degrees may solve a lot of the problem.

If memory serves, ljk is actually not that far from Orlando. I suggested in a PM that if he's uncomfortable with tuning the scanners himself, he might want contact Pangolin and see if Bill has some time to give him a tour of the home office. If it works out, he could pick up a few pointers from Bill about scanners while he's there.

Adam

[ljk]

Well I am getting a little closer now. I have the ILDA test pattern pretty close but the Lasr Media pattern needs a lot of help.

This laser is using TTL not analog for blanking, waiting for new toys from UPS.

Scan rate is set for 30K with 8 deg angle.

Any thoughts on what I need to do to get Laser Media picture adjustment correctly.

[DZ]

It's looking much better LJ, at this point, you're going to have to start playing around with HFD and LFD and the laser media test pattern should start to clean up. Check your email.

[buffo]

Hi LJK!

Sorry for the late reply. Been away for a little while.

The ILDA test pattern looks very good - much better than before. You are almost there. The problem now is that you have the scanners running at slightly different speeds. This is tricky to adjust, and in the end you may have to live with a slight artifact in either the LaserMedia pattern or the ILDA test pattern. (If you have a choice, you'd rather have a perfect LaserMedia test pattern and a slight artifact on the ILDA test pattern.)

Have you tried turning off the blanking yet? (That's mentioned near the end of my scanner tuning tutorial) That will help you get a better handle on the fine adjustments needed to make your scanners perfect.

Note that *any* change in damping (HF or LF) or gain will change the scanner speed and thus will affect the separation of the retrace lines on the laser media test pattern. Often times you're only talking about a small adjustment. So be patient, be methodical, and see what you can do.

One thing to try is to adjust the gain on one scanner while watching the lasermedia test pattern. If you go UP on the speed and the lines come closer together, then you know that you've picked the slower of the two scanners. Then try to split the difference between the two amps. (That is, speed the slow amp up a little and slow the fast amp down by the same amount.) Now go back to the ILDA test pattern and adjust the damping until it looks right, then flip back to the Lasermedia test pattern again.

You may need to do this a couple times. Make *small* adjustments. If you just can't get it right, try walking *both* amps back down a few steps and then start bringing the gain back up again. Often times if you can't get a smooth circle *and* a decent lasermedia test pattern, it's because you have too much gain (you're too high up the stairs) and the excessive damping needed to control all that extra gain is screwing up your lasermedia test pattern. Basically, you've over-shot the optimal tuning point.

This is where having the blanking turned off will help you. Look at that long, normally-blanked line that comes down to the bottom on the ILDA test pattern and watch how it moves with slight adjustments of LF and HF damping. Then rotate the test patern 90 degrees and check it on the other amp. That should get you on the right track...

Any word yet on your possible visit to Orlado to tour the Pangolin office?

Adam

[allthatwhichis]

Wow, just the '?' I needed answered... What is better, perfect ILDA or Laser Media patter.

[buffo]

Yeah, I had a long discussion with Bill about that exact question a while back. The reasoning goes like this:

Retraced lines (or more likely, closely-spaced diagonal lines drawn in different directions) are far more likely to be encountered in your ILDA file library than a large ballistic circle like you see at the center of the ILDA test pattern. Thus, if the ballistic circle is slightly oval, that's OK. Yes, it means that the scanners are running at slightly different speeds, but *only when they are ballistic*. There are lots of things that can affect scanner speed when they are running under absolute maximum acceleration.

Whereas if you have separation on the retraced lines in the Lasermedia test pattern, that means your scanners are running at different speeds even when they are *not* ballistic - that is, even when they are *not* under maximum accelleration. Since this is the more common mode of operation, it is the one that should be perfect, not the ILDA circle.

Make sense?

Adam

[ljk]

Thanks Buffo, I am working out timing to see Bill looks like it will be late in January. I will adjust more tonight.