Teletect Dither

To dither is to add a controlled pattern of noise before reducing color depth, so that the eye averages neighboring pixels into tones the palette doesn’t contain.

Control Page (Switch 11) selects which page the six knobs edit. Each page keeps its own saved values. When you change pages, each knob is locked at its saved value until you turn it to (or past) that value, so nothing jumps. The switches and the Mix Step fader work the same on both pages.

On the Edit page the three palette colors line up in three columns: saturation on top, brightness below. Knob settings take effect at the start of the next field or frame.

Most knobs are stepped. The LCD shows their position as one of eight steps, 0/7 to 7/7.

Perform: the hue of palette color 1, one of eight positions around the color wheel. Edit: the saturation of color 1, from neutral (0/7) to full (7/7) in eighths.

Perform: the hue of palette color 2. Edit: the saturation of color 2.

Perform: the hue of palette color 3. Edit: the saturation of color 3.

Perform: the dither amount, in halving steps from full strength (7/7) down to off (0/7): 100%, 50%, 25%, 12.5%, 6.25%, 3.125%, 1.5625% and 0%. At 0/7 there is no dither at all, just a flat reduction to the palette, which gives posterized bands. Edit: the brightness of palette color 1, in eight steps from near black to near white.

Perform: input contrast before dithering, from 50% (0/7) through unchanged (4/7) to 137.5% (7/7), in 12.5% steps. Edit: the brightness of palette color 2.

Perform: a smooth brightness offset applied to the input after contrast and before dithering. Center is unchanged. Edit: the brightness of palette color 3, in eight steps. The LCD still shows the knob position as a percentage on the Edit page.

Diffuse carries each pixel’s rounding error onto the next line, for grainy, organic texture with some visible streaking. Bayer adds a fixed threshold pattern instead, for a regular crosshatch with no feedback between pixels.

The size of the Bayer pattern. 4x4 is coarser and more graphic; 8x8 gives smoother gradients. It has no effect in Diffuse mode.

Palette reduces the picture to black, white and your three palette colors. RGB quantizes red, green and blue separately and ignores the palette.

This switch means something different in each color mode, so both meanings are on its label: the number is the RGB color count and the word is the palette selection type.

Selects which page the six knobs edit. See Perform and Edit pages above.

Mix Step blends the original and dithered pictures in sixteenths. Only 16/16 produces purely palette or RGB colors; lower settings let the original picture show through.

When a pixel is rounded to the nearest available color, the difference (the error) is not thrown away. Teletect Dither passes it to the next line, split between the pixels below-left, below and below-right. Neighboring pixels then round the other way often enough that, viewed from a distance, the average matches the original tone. Because the error only travels down, not sideways, the texture has a slight vertical streak compared with the classic Floyd–Steinberg pattern.

Bayer dither compares each pixel against a threshold taken from a repeating 4×4 or 8×8 grid. The result is a regular pattern, with no error carried between pixels, that is very stable on moving images.

In Palette mode with Nearest, each pixel picks whichever of the five palette colors is closest, weighting brightness twice as heavily as color. With Forced, palette slots are chosen by brightness bands alone, so you can map shadows, midtones and highlights to any colors you like, regardless of the input’s hue.