Need help understanding Chromapure Primary and Secondary colors - AVS Forum
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post #1 of 7 Old 10-18-2013, 05:35 AM - Thread Starter
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Hi all,

I just started learning Chromapure and am on my third attempt at calibrating my BenQ W1080st before moving on to my main projector. I understand the concepts of nailing down the greyscale, but I am confused when it comes to getting the color gamut right due to the differences between Color Decoding and Color Management.

From what I understand from the help documentation in Chromapure, if your projector or TV has a CMS to not worry with color decoding and jump straight into the CM section. I've read through several articles that states when adjusting RGB primaries to only worry with eliminating errors with the brightness and for the secondary colors to worry about hue and saturation (in this order.) Does this mean that if you have a full CMS that offers Hue/Gain/Saturation for both primary and secondary colors the rule should be ignored, or would the goal then be to minimize errors for all 3 utilizing the best combination possible to get there?

For my last attempt I did the latter and selected HSL/REC709 and utilized Gain/Hue/Saturation for all the colors and used Chromapure's % meter to get the lowest possible number. I did notice there was a direct correlation with these settings and adjusting hue brought down saturation and gain would sometimes impact saturation as well. The outcome was overall good, but my blues appear to be very oversaturated which is leading me to believe I did something wrong; in particular, I was confused because on some colors like red and magenta I could never get hue and saturation to 0 as adjusting one would bump the other into the negative or positive range. Is there a particular dE I should shoot for when adjusting the colors or is it the lower the better regardless of what it takes to get there?

Thanks for any help or advice in advance!
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post #2 of 7 Old 10-18-2013, 05:43 AM
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This article my help http://www.tlvexp.ca/2013/03/color-management-system-pie-eat-half-or-all/
There are also training videos on Michael's site you cam pay for. I would venture a bet they would answer all your questions on the subject. Poke around his site, there is a lot of very useful info for free as well. You may need to register to read some of it.
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post #3 of 7 Old 10-18-2013, 06:29 AM
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Greetings

I did away with the whole registration aspect to the site. All articles are either available for all to access or they are password protected (and you'll know when you see those.)

regards

Michael Chen @ The Laser Video Experience
ISF/THX/TLV Video Instructor
The Video Calibration Education Hub - www.TLVEXP.com

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post #4 of 7 Old 10-18-2013, 06:57 AM - Thread Starter
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Thanks air, I will check out Michael's site a little later today.
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post #5 of 7 Old 10-18-2013, 08:56 AM
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Greetings

The video series calibration content is more thorough than you would find in an ISF class or even a THX class. But it can't compress 25 years of experience into such a time frame ... nothing can.

regards

Michael Chen @ The Laser Video Experience
ISF/THX/TLV Video Instructor
The Video Calibration Education Hub - www.TLVEXP.com

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post #6 of 7 Old 10-18-2013, 10:44 AM - Thread Starter
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Originally Posted by Michael TLV View Post

Greetings

The video series calibration content is more thorough than you would find in an ISF class or even a THX class. But it can't compress 25 years of experience into such a time frame ... nothing can.

regards

Hey Michael,

I decided to take advantage of all your great knowldege and have been reading through your various beginners articles first and will progress into the calibration video content.

Thank you for offering such a wonderful site!
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post #7 of 7 Old 10-27-2013, 06:47 PM
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Quote:
Originally Posted by jmalto View Post

Hi all,

I just started learning Chromapure and am on my third attempt at calibrating my BenQ W1080st before moving on to my main projector. I understand the concepts of nailing down the greyscale, but I am confused when it comes to getting the color gamut right due to the differences between Color Decoding and Color Management.

From what I understand from the help documentation in Chromapure, if your projector or TV has a CMS to not worry with color decoding and jump straight into the CM section. I've read through several articles that states when adjusting RGB primaries to only worry with eliminating errors with the brightness and for the secondary colors to worry about hue and saturation (in this order.) Does this mean that if you have a full CMS that offers Hue/Gain/Saturation for both primary and secondary colors the rule should be ignored, or would the goal then be to minimize errors for all 3 utilizing the best combination possible to get there?

For my last attempt I did the latter and selected HSL/REC709 and utilized Gain/Hue/Saturation for all the colors and used Chromapure's % meter to get the lowest possible number. I did notice there was a direct correlation with these settings and adjusting hue brought down saturation and gain would sometimes impact saturation as well. The outcome was overall good, but my blues appear to be very oversaturated which is leading me to believe I did something wrong; in particular, I was confused because on some colors like red and magenta I could never get hue and saturation to 0 as adjusting one would bump the other into the negative or positive range. Is there a particular dE I should shoot for when adjusting the colors or is it the lower the better regardless of what it takes to get there?
Yes, the Color Decoding module is only for displays that have no CMS. They might have just Color and Tint controls or even primary luminance and secondary hue controls in the service menu. If you have a full-featured CMS, then ignore this.

I don't know where you got that advice, but it is really, really wrong. When adjusting RGB primaries, you ALWAYS need to pay attention to hue, saturation, and luminance. Adjusting luminance only is nuts. As a matter of fact color decoding errors only affect the luminance of primary colors. However, not all primary color errors are due to color decoding issues. See our web site for discussion of color decoding.

http://www.chromapure.com/colorscience-decoding.asp

Do levels first, then grayscale, then gamma, then primary colors, and last secondary colors. Go back and remeasure everything after finishing each. Calibration is a reiterative process. Seek the lowest dE possible on all pri/sec colors. To get this you must pay attention to all three points of adjustment. There may be--as you have discovered--some interaction between these controls, but that's normal. Just get the lowest dE you can.

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
Springfield, MO

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