Calibratiing with the Lumagen HDP built in test Patterns - AVS Forum
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post #1 of 11 Old 08-21-2005, 05:11 PM - Thread Starter
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FYI, the attached file is a mini-howto I wrote based on input from the Lumagen guys and a thread on their site. (Original thread here). The attached document explains some proper methods to calibrate a projector connected digitally to a Lumagen HDP using the HDP's internal grayscale test patterns.

AKA, "I love my free Lumagen mini-signal generator"

This is specific to my setup, but IMO lays a foundation for other inputs as well.

Hope it is helpful to someone else. Scott

 

Lumagen Calibrate.doc 42.5k . file
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post #2 of 11 Old 08-22-2005, 10:06 AM
 
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Greetings,

I am very interested in the whole BTB picture info/calibration issue.

I would like to conjecture, it would be wrong to refer to (real picture) data to
go below (0% IRE). Implying, a paradox concerning having the ability to code
said (-4IRE) BTB bar altogether?

There is room for Poynton's (special case flow), but is not implemented or used that I know of?

Can someone please explain? How can anyone report "seeing" the BTB bar that is coded in the Avia/DVE grey ramps?

Thanks in advance,
thomas
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post #3 of 11 Old 08-22-2005, 10:23 AM - Thread Starter
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Thomas:

The terms I used of -4 IRE I'm sure are incorrect. As I mentioned in the document, the text was in "my words" mostly to convey to myself what I was covering :). I was just pointing out the thing being displayed is below video black. Perhaps better wording would be 4% above/below video black and video white. It has to do with PC vs video levels and digital signals. 0 IRE (at video levels) is not 0/0/0 RGB digital levels. I'm no expert on the subject and would defer to the experts monitoring the aforementioned thread becasue of it.

The best place to ask about those deails is in the thread I linked in the document:
"For a extensive discussion/education of video vs PC levels and source settings, blacker than black, whiter than white, etc., see:
http://www.avsforum.com/avs-vb/showthread.php?t=494606


The author of that thread can best speak to the issue in perfect detail. And he's subscribed becasue he has answered my questions, too.

P.S. no need to send PM's asking for thread participation. If I posted in a thread I'm subscribed to it, unless it's very, very old.

Best, Scott
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post #4 of 11 Old 08-22-2005, 11:18 AM
 
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Quote:
Originally Posted by GetGray
Thomas:

The terms I used of -4 IRE I'm sure are incorrect. As I mentioned in the document, the text was in "my words" mostly to convey to myself what I was covering :). I was just pointing out the thing being displayed is below video black. Perhaps better wording would be 4% above/below video black and video white. It has to do with PC vs video levels and digital signals. 0 IRE (at video levels) is not 0/0/0 RGB digital levels. P.S. no need to send PM's asking for thread participation. If I posted in a thread I'm subscribed to it, unless it's very, very old.

Best, Scott
Sorry, should have realized you would see a post on a thread you started :)

Scott: I can't understand ie (0% stimuli) or 0 setup "not" being = 0/0/0..and if this is the case, what offset do I need to translate for PC (RGB) color space?
After all (0mV) is (0mV), or am I just missing something altogeher? What is the reference for the so called BTB bar? I need a reference to measure it!

There seems to be some confusion on the expansion from 8 bit (235/16) to
PC with (255/000). If "black" is (0%) for one, then should it be (0%) for PC?

thomas
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post #5 of 11 Old 08-22-2005, 12:02 PM - Thread Starter
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I only see the practical application of the issue. What I described works properly. That's a question for the more general thread linked above, not specific to using the Lumagen HDP test patterns. Ask Chris there, he's got a firm handle on it.
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post #6 of 11 Old 08-22-2005, 01:30 PM
 
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FWIW: If Chris has his hand on the "gamma" knob..Then you would be better off
speaking with someone else on the subject :)

thomas
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post #7 of 11 Old 08-22-2005, 04:55 PM
 
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get gray, you should rest assured in your methods, I skimmed through your document and it is good. trbrunet has not grasped the presence of this footroom and headroom, the digital range, nor the interface between digital and analog video.

Quote:
There seems to be some confusion on the expansion from 8 bit (235/16) to
PC with (255/000). If "black" is (0%) for one, then should it be (0%) for PC?
I have explained to you, that 0% stim, or black, is coded at level 0 with PC Graphics levels, and is coded at level 16 when following Video standards for video material. This is in the digital realm. Both 0 and 16 can represent 0% stim, or black, depending on the encoding standard used. For video it should always be at level 16, and not 0.

As I explained to you before, when digital is converted into analog, it depends on the source device what voltage(IRE) these values will become.

Quote:
Can someone please explain? How can anyone report "seeing" the BTB bar that is coded in the Avia/DVE grey ramps?
If your playback system does not clip the data, you can temporarily raise your black level, and decrease your white level to ensure that the entire signal is visible within the contrast range of your display, and you can see the BTB and peak white portions of the signal range. As I told you before, you must use DVE, DVE PRO, or Avia PRO for this testing. Avia's pattern elements are limited to the 16-235 range, there are no elements outside these bounds. Avia PRO has full-range patterns.
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post #8 of 11 Old 08-22-2005, 05:12 PM
 
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Quote:
Originally Posted by ChrisWiggles
get gray, you should rest assured in your methods, I skimmed through your document and it is good. trbrunet has not grasped the presence of this footroom and headroom, the digital range, nor the interface between digital and analog video.
I have a Tektronix WF monitor... & When I scope a smpte259/292 signal. I see no information below blanking level ie the reference level for "picture information"

If I can't measure it, then how does your projector/CRT see it? When you can answer this, I will inturn call "Tektronix Labs" for you, and have them make a new
graticule for the new BTB information.. I'm guessing it will go something like (-1,-2,-3,-4IRE)? :)
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post #9 of 11 Old 08-22-2005, 05:15 PM - Thread Starter
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Chris: Thanks for taking the time to look it over. Much appreciated. The Lumagen guru's also cooberated my story :)
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post #10 of 11 Old 08-22-2005, 05:25 PM - Thread Starter
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thomas: I was trying before to be subtle and thus polite, twice. I suppose I need to be blunt. Please, start your own thread.

Duke out your understandings there. The point of starting your own relevant thread is more people who are interested in your subject will participate with you. Here on my thread, you'll be missing out on all the folks who I'm sure will be tickled to participate in your interest. Maybe you and Tektronix can teach them all something and get them straightened out. But do it in your thread.

What I've posted here is what the manufacturer (and other's regarded as in-the-know) agree is the proper way to calibrate specifically using a Lumagen HDP scaler. This is meant for HDP scaler owners or potential owners. It's focus is on using internally generated test patterns of the HDP.

Please, stay on topic on my thread, or go the the forum of your choice and press the button that says "New Topic". Call it "why me and my tecktronix say everyone else is wrong" or whatever. I promise not to hijack it.

Other's: Don't feed.
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post #11 of 11 Old 08-23-2005, 01:15 PM
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Thanks for the mini-how to. I employed many of the ideas you have here along with smart; but there are some things here that are new specific to the Lumagen HDP.

Will try them this weekend and see if I can improve my setup ;).
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