CRT:CRT Color Calibration Guide: Difference between revisions

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(Created page with "This guide only applies to NTSC sets. == Requirements == * A good colorimeter: ** ColorMunki Display ** X-Rite i1 Display ** X-Rite i1 DisplayPro ** ColorHug (Open Source) ** ColorHug 2 (Open Source) ** HCFR Colorimeter ** [https://www.argyllcms.com/doc/instruments.html Any colorimeter listed here] ** It's recommended to avoid Spyder products, as the colorimeters themselves seem to drift after a few years and require recalibration. * A PC video card or downscaler and c...")
 
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#* On the Standard drop-down menu, select `SDTV - REC 601 (NTSC)`.
#* On the Standard drop-down menu, select `SDTV - REC 601 (NTSC)`.
#* Select the "Display Gamma (power law)" radio button.
#* Select the "Display Gamma (power law)" radio button.
#* Look through your CRT set's service manual and see if there is any specified calibration targets. For instance, it might say "if you have 100 nits at 2.4 gamma, 20 IRE should be at 2.7 nits" or some other specific values. If so, enter the specified gamma number under "Power Law Gamma". If no specific values provided in manual, set gamma to `2.3` and your 100 IRE target will be 3 nits. Click Apply.
#* Look through your CRT set's service manual and take note if there is any specified calibration targets. For instance, it might say that "if at a gamma setting of 2.4, 100 IRE is 100 nits, then 20 IRE should be at 2.7 nits" or some other specific values. If so, enter the specified gamma number under "Power Law Gamma" and click Apply.
#** If no specific values are provided in the manual, set gamma to `2.3` and your 100 IRE target will be 120 nits and your 20 IRE target will be 3 nits. This appears to be the values most Sony professional models are calibrated to.  
# Click the Advanced tab. Look at the service manual to determine when your CRT model was first produced. Use that to determine the Color Difference Formula to use under Refs > Advanced tab. Different Color Difference Formulas were established in 1976, 1994, 2000 - so choose the option previous to the year your monitor was produced (i.e. `CIE94` for a monitor made in 1998). Click Apply and OK.
# Click the Advanced tab. Look at the service manual to determine when your CRT model was first produced. Use that to determine the Color Difference Formula to use under Refs > Advanced tab. Different Color Difference Formulas were established in 1976, 1994, 2000 - so choose the option previous to the year your monitor was produced (i.e. `CIE94` for a monitor made in 1998). Click Apply and OK.
# Click the edit button in the Generator section in the top-right of the window. Select your monitor on the target screen. Change "Image Area (%)" to 25 and click OK.
# Click the edit button in the Generator section in the top-right of the window. Select your monitor on the target screen. Change "Image Area (%)" to 25 and click OK.


== Calibrating Colors ==
If you have 120 nits at 100 IRE and a 2.3 gamma, your 20 IRE target will be about 3 nits.


First, you will calibrate greyscale, followed by Red and Blue - repeatedly checking greyscale calibration as you go. If everything ends up perfect, the white triangle in the CIE diagram will match up with the black triangle.
== Calibrating Greyscale ==


{{Note|You generally can't change green values on CRT sets, so if green is far off-target in the CIE diagram, you will need to fix color purity either through menu options (for very high end sets) or through adjusting the rings on the yoke of the set. It may also be caused by a magnetic issue that can be fixed with an external degaussing.}}
First, you will calibrate greyscale to make sure the brightness and contrast are at the correct level for color calibration.


# Mount the colorimeter in the center of your screen.
# Mount the colorimeter in the center of your screen.
# Click the "Measure gray scale" button, and look at the red/yellow/red results for DeltaE. You want a low (<2.0) DeltaE for every value. Anything below a value of 1.0 is not really visible by the naked eye.
# Click the "Measure gray scale" button, and look at the red/yellow/red results for DeltaE to see how well calibrated your set is.
#* You are wanting a low (<2.0) DeltaE for every value. Anything below a value of 1.0 is not really visible by the naked eye.
#* Below 0.5 for all values isn't really obtainable for anything but later professional or broadcast monitors.
#* Below 0.5 for all values isn't really obtainable for anything but later professional or broadcast monitors.
# Click the "Measure primary and secondary colors" button.  
# Click the "Measure primary and secondary colors" button.
#* Reds will generally always run a bit higher.
# Click the "100" column header (% White) on the table to select 100 IRE and click the "Run or stop continuous measures". The screen will display a white image at 100% brightness. Change the contrast value on your CRT set until the "Y" value in the 100 IRE column matches the value the service manual specified for 100 IRE.
# Select the "100" IRE header (% White) and click the "Run or stop continuous measures". The screen will display a white image. Change contrast values to try and get "Y" value to try and match "Y target". The "Y target" value will change based on calculations based on the peak white value it observes.
$* If your service manual did not specify a value, target 120 nits.
# Click the "20" column header to select 20 IRE. Change brightness value to try and get "Y" value to try and match the value the service manual specified for 20 IRE.
$* If your service manual did not specify a value, target 3 nits.
# Repeat the two above steps until you are as close as possible to your target values for 100 IRE and 20 IRE. You will likely need to repeat these steps quite a few times.
 
== Calibrating Color ==
 
Next, you will calibrate red and blue color - repeatedly checking greyscale calibration as you go. If everything ends up perfect, the white triangle in the CIE diagram (current state) will match up with the black triangle (target state).
 
{{Note|You generally can't change green values on CRT sets, so if green is far off-target in the CIE diagram, you will need to fix color purity either through menu options (for very high end sets) or through adjusting the rings on the yoke of the set. It may also be caused by a magnetic issue that can be fixed with an external degaussing.}}


////////////
Select the 20 IRE table header once again. Take a look at the "Current Measure" table at the bottom half of the screen and note the R (red), G (green), and B (blue) values. The G value should be close to your "Y target" for 20 IRE. You are aiming to make R and B values equal to the G value.


# Repeat above step for 20 IRE to try and get the Y value to be 3 nits unless otherwise specified in the manual.
# Repeat the steps for red and blue drive and cutoff.
# Repeat the steps for red and blue drive and cutoff.


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| Brightness ||  
| Brightness ||  
|-
|-
| Rec601 ||  
| Rec601 || The Color Space standard for NTSC Standard Definition Television (SDTV).
|-
|-
| Rec709 ||  
| Rec709 ||  
|-
|-
| Nits || Brightness unit (candelabra per square meter?) How much light is being output for a certain area.
| Nits || Brightness unit (candelabra per square meter?) representing how much light is being output for a certain area. This is the "Y" value in HCFR.
|-
|-
| IRE || (% of whiteness?)
| IRE || A unit representing the percentage of whiteness of a signal in a NTSC composite signal. Stands for "Institute of Radio Engineers". This is the header row in the main table in HCFR.
|-
|-
| DeltaE ||  
| DeltaE || The difference between your current nits value (Y value) and the target nits value (Y target).
|-
|-
| NTSC 3.58 ||  
| NTSC 3.58 ||  
|-
|-
| Y value || Current nits value
| Y value || Current nits value.
|-
|-
| Y target || Calculated target nits value
| Y target || Calculated target nits value. At 100 IRE, this will match the current nits value observed.
|}
|}


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Questions:
Questions:
How to set HCFR to output 480i / the right screen?


You specifically chose white point D65, right? What determines what option to set?
You specifically chose white point D65, right? What determines what option to set?
List of good model colorimeters to use?
I missed the beginning of the stream. What settings should be set besides Rec609 and the correct Color Formula?


What is a "full tilt boogie"?
What is a "full tilt boogie"?

Revision as of 05:02, 13 April 2022

This guide only applies to NTSC sets.

Requirements

  • A good colorimeter:
    • ColorMunki Display
    • X-Rite i1 Display
    • X-Rite i1 DisplayPro
    • ColorHug (Open Source)
    • ColorHug 2 (Open Source)
    • HCFR Colorimeter
    • Any colorimeter listed here
    • It's recommended to avoid Spyder products, as the colorimeters themselves seem to drift after a few years and require recalibration.
  • A PC video card or downscaler and cables capable of outputting 480i to your CRT set. Use the best option available to you (i.e. HDMI > RGBS > s-video > composite). Do not calibrate using 240p as it will be incorrect, even if you are only using the set for 240p content.
  • A PC capable of running HCFR for Windows

HCFR Setup

  1. Install HCFR for Windows.
  2. Under the Information section, select "CIE Diagram" from the drop-down menu.
  3. Click the "Refs" button on the right-hand side.
    • On the Standard drop-down menu, select SDTV - REC 601 (NTSC).
    • Select the "Display Gamma (power law)" radio button.
    • Look through your CRT set's service manual and take note if there is any specified calibration targets. For instance, it might say that "if at a gamma setting of 2.4, 100 IRE is 100 nits, then 20 IRE should be at 2.7 nits" or some other specific values. If so, enter the specified gamma number under "Power Law Gamma" and click Apply.
      • If no specific values are provided in the manual, set gamma to 2.3 and your 100 IRE target will be 120 nits and your 20 IRE target will be 3 nits. This appears to be the values most Sony professional models are calibrated to.
  4. Click the Advanced tab. Look at the service manual to determine when your CRT model was first produced. Use that to determine the Color Difference Formula to use under Refs > Advanced tab. Different Color Difference Formulas were established in 1976, 1994, 2000 - so choose the option previous to the year your monitor was produced (i.e. CIE94 for a monitor made in 1998). Click Apply and OK.
  5. Click the edit button in the Generator section in the top-right of the window. Select your monitor on the target screen. Change "Image Area (%)" to 25 and click OK.

If you have 120 nits at 100 IRE and a 2.3 gamma, your 20 IRE target will be about 3 nits.

Calibrating Greyscale

First, you will calibrate greyscale to make sure the brightness and contrast are at the correct level for color calibration.

  1. Mount the colorimeter in the center of your screen.
  2. Click the "Measure gray scale" button, and look at the red/yellow/red results for DeltaE to see how well calibrated your set is.
    • You are wanting a low (<2.0) DeltaE for every value. Anything below a value of 1.0 is not really visible by the naked eye.
    • Below 0.5 for all values isn't really obtainable for anything but later professional or broadcast monitors.
  3. Click the "Measure primary and secondary colors" button.
  4. Click the "100" column header (% White) on the table to select 100 IRE and click the "Run or stop continuous measures". The screen will display a white image at 100% brightness. Change the contrast value on your CRT set until the "Y" value in the 100 IRE column matches the value the service manual specified for 100 IRE.

$* If your service manual did not specify a value, target 120 nits.

  1. Click the "20" column header to select 20 IRE. Change brightness value to try and get "Y" value to try and match the value the service manual specified for 20 IRE.

$* If your service manual did not specify a value, target 3 nits.

  1. Repeat the two above steps until you are as close as possible to your target values for 100 IRE and 20 IRE. You will likely need to repeat these steps quite a few times.

Calibrating Color

Next, you will calibrate red and blue color - repeatedly checking greyscale calibration as you go. If everything ends up perfect, the white triangle in the CIE diagram (current state) will match up with the black triangle (target state).

Exclamation-circle-fill.svgYou generally can't change green values on CRT sets, so if green is far off-target in the CIE diagram, you will need to fix color purity either through menu options (for very high end sets) or through adjusting the rings on the yoke of the set. It may also be caused by a magnetic issue that can be fixed with an external degaussing.


Select the 20 IRE table header once again. Take a look at the "Current Measure" table at the bottom half of the screen and note the R (red), G (green), and B (blue) values. The G value should be close to your "Y target" for 20 IRE. You are aiming to make R and B values equal to the G value.

  1. Repeat the steps for red and blue drive and cutoff.


Definitions

Term Definition
Phosphors
P-22
SMPTE-C
White Point (D65, etc)
Contrast
Brightness
Rec601 The Color Space standard for NTSC Standard Definition Television (SDTV).
Rec709
Nits Brightness unit (candelabra per square meter?) representing how much light is being output for a certain area. This is the "Y" value in HCFR.
IRE A unit representing the percentage of whiteness of a signal in a NTSC composite signal. Stands for "Institute of Radio Engineers". This is the header row in the main table in HCFR.
DeltaE The difference between your current nits value (Y value) and the target nits value (Y target).
NTSC 3.58
Y value Current nits value.
Y target Calculated target nits value. At 100 IRE, this will match the current nits value observed.

Tips and Troubleshooting

If on a 50% gray screen you are seeing spots that are discolored, try doing an external degauss.


Questions:

You specifically chose white point D65, right? What determines what option to set?

What is a "full tilt boogie"?

Calibrating PAL/SECAM? There's a Color Space Standard option for it.

When to use Rec709?

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