CRT:CRT Color Calibration Guide

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 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.
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.

Calibrating Colors

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.

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.

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. 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.
   • 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.
   • Reds will generally always run a bit higher.
4. 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.

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1. Repeat above step for 20 IRE to try and get the Y value to be 3 nits unless otherwise specified in the manual.
2. 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
Rec709
Nits	Brightness unit (candelabra per square meter?) How much light is being output for a certain area.
IRE	(% of whiteness?)
DeltaE
NTSC 3.58
Y value	Current nits value
Y target	Calculated target nits value

Tips and Troubleshooting

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

Questions:

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

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"?

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

When to use Rec709?