Hawes Mechanical Television Archive by James T. Hawes, AA9DT
Colorize Your Mechanical TV System, Part 1

Continuous vs. Sequential Color

Farbfernseher: TV displaying color bars

Convert to Color Today! If you have a source of color programming, you can convert your monochrome set to color. This page details the changes that you need to make. I describe a continuous color system. These steps won't work for field-sequential color. True, field-sequential color uses less bandwidth than continuous color does. But there's a cost. With rapidly moving subjects, field sequential color causes color ghosts. These ghosts are really "color flicker."

Flicker. Field-sequential color also reduces frame rate or vertical definition by two-thirds. If your frame rate is only 12.5 fps, you'll certainly notice the flicker! These problems are why continuous color is the preferred option for mechanical TV.

A Continuous Color Method

A continuous color project offers you several colorizing choices. Start by deciding on a two-color, discrete three-color, or derived three-color system. If naturalistic color isn't a goal, you have one more option: Pseudocolor.

  • Two-color systems offer economical, simplified full-color pictures. If you have limited space for additional circuitry, use a two-color circuit. Another reason to consider two-color: Your power supply. Does it put out enough current to power three LED drivers? Does it put out enough voltage to drive one or more blue LEDs? Remember, blue LEDs take more voltage than red LEDs take. A red and cyan system might avoid these current and voltage problems. Learn more about two-color TV systems: Click 2-Color TV.

  • Discrete three-color systems offer full-color pictures that might include a broader range of colors (gamut). Three-color circuits also offer more controls. More controls is one advantage of increasing circuit complexity by 33 percent. On the flip-side, more controls means more adjustment time and more problems. Your choice.

  • Derived three-color systems are the happy medium between two-color and discrete three-color systems. Additive primary colors all relate on the color wheel. The same is true for electronic color that we use in television. Mix any two primaries to form a complementary color. Invert the complementary color, and you'll acquire the third primary color. That is, the complement of the third color signal lies somewhere between the other two color signals.

  • Pseudocolor systems start with a monochrome signal and interpolate colors. Pseudocolor systems accomplish this end by assigning hue and saturation values to intensity values. Some medical imaging and weather mapping systems use pseudocolors. In these types of imaging, the number of discernable gray tones may be small. Yet in pseudocolor images, an observer can detect color patterns where corresponding gray patterns might be elusive.

The Camera

  1. If you picked the pseudocolor option, please skip camera changes. Otherwise, proceed.

  2. Start with the camera. Duplicate your video preamplifier circuit once for two-color TV. For three-color TV, add two more video preamplifiers.

  3. Add color filters to the pickup devices: Red for the red circuit, and so forth. With two-color TV, you'll achieve the best color reproduction if you choose complementary colors. Some complementary colors are probably better than others. For suggestions, see the table. I've organized table color choices by how well they're likely to perform. The top colors, orange and blue-cyan, are the basis for the NTSC color model. These colors render flesh tones for all races particularly well. Also, the human eye is more sensitive to orange and blue-cyan than to their opposites. These opposites are magenta and green-yellow.

  4. 2-Color TV with Complementary Colors
    Orange Blue-Cyan Yes*
    Red Cyan Yes
    Magenta Green Maybe
    Yellow Blue No
    *Note: Most common choice, due to best flesh tone rendition.

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WARNING. This is your project. Your achievement is entirely yours. I assume no responsibility for your success in using methods on these pages. If you fail, the same is true. I neither make nor imply any warranty. I don't guarantee the accuracy or effectiveness of these methods. Parts, skill and assembly methods vary. So will your results. Proceed at your own risk.

WARNING. Electronic projects can pose hazards. Soldering irons can burn you. Chassis paint and solder are poisons. Even with battery projects, wiring mistakes can start fires. If the schematic and description on this page baffle you, this project is too advanced. Try something else. Again, damages, injuries and errors are your responsibility.
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