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Topic: Difference between dithering and halftone

Posted under General

Serlo

Up until now I understood the difference between the two terms being merely that dithering was one way to produce a halftone gradient. That we have 2 different tags and wiki pages suggests that at least danbooru defines them differently, but I couldn't understand how they tagged different concepts from the current wiki pages. They seem to describe the same thing twice, but I might be being dense.

Wiki:Halftone
Halftone is the reprographic technique that simulates continuous tone imagery through the use of equally spaced dots of varying size"

Wiki:Dithering
A method to create the illusion of colour shading or blending; through varied spacing of different coloured pixels from a limited pallete.

Updated by 葉月

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  • r0d3n7z

    My understanding [someone correct me if I'm wrong] is that dithering applies more to digital color quantization, whereas halftone originates from the printing process, and reproducing gradients or a wide range of colors using very few colors (mono, CYMK).

    dithering: post #931673, post #931098, post #441501

    halftone (color): post #737146, post #739272, post #673529
    halftone (mono): post #935585, post #835180, post #982404

    I saw some cases that I'm not entirely sure about myself, like:

    Looks like there are mistagged posts in polka dot and moire too.

    Updated by r0d3n7z

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  • ghostrigger

    i'm no expert here but i'll add my understanding as well. i first thought they're the same until somebody corrected my edits and brought me to the wiki pages, though i forgot the posts involved.

    halftone - seems to be used at least in 2 cases. one, would be in monochromatic comics used to create an illusion of "color", shade or shadow. second, would be a "zoom-in down to the pixels" scenario. something like you put a newspaper sheet up close, very very close to your eyes. though the wiki states equally spaced dots of varying sizes, sometimes it's impossible to check because it's so small. easier posts would be those if you see there's a progression in size.

    dithering - if you happen to play dos games before, if the post gives you that "feel", this comes to my mind.

    however, this is just me. i checked monochrome halftone has 5 pages only. while monochrome dithering has 2 pages. the dithering wiki states colored pixels from a limited palette. don't know if this is just mistagging though.

    ps: post #1133339 - not 100% sure myself if it's halftone. in any case, i think it's too small to be a polka dot, i first thought it's snow. but if i've mistaken please correct me. thanks.

    Updated by ghostrigger

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  • 葉月

    Dithering and halftone are fundamentally different techniques, as they approach the same problem from the opposite ends.

    • Dithering uses uniform-size dots (or pixels in case of digital dithering), and varies their position to simulate more shades with fewer base colours. It's the technique used in screen images and inkjet printers.
    • Halftone uses uniformly-spaced dots, and varies their size to simulate the missing shades. You probably know it as the newspaper photo appearance, because newspapers tend to be printed on cheaper paper that cannot accommodate very fine dots, so the halftones are readily noticeable.

    For missing hues a digitally dithered image would have different colour pixels alternating in some pattern, with the colours not necessarily being base colours, but rather whatever colours expressible directly by the screen can be mixed to achieve the best output hue. OTOH, halftone images apply a constant and separate pattern for each base colour, each matrix offset by a fraction of the pattern size, to give a more uniform result appearance. There is a single plate (ie. pattern) for each base colour, but "base colour" need not correspond to the conventional meaning of the term, as long as applicable inks can be applied. So for example, gold metallic, yellow and blue are a perfectly acceptable set of halftone plates. The number of base inks is always strictly defined for any given print, and a small number on the order of 2-6.

    For danbooru purposes, the halftone in question will nearly always be a significantly magnified version, highlighting the separate dots aspect of the technique, and itself faked on screen by using digital filters.

    Lastly, screntone is sort of a prepackaged halftone which can be applied to a physical sheet of paper (because it's designed to be transferrable). Screentones differ, however, in the fact they don't necessarily use uniformly round dots varying in size, the way halftones do, but rather employ a variety of geometric patterns. The familiar effect from manga pages is the result of applying screentones.

    Updated by 葉月

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  • Serlo

    葉月 said:
    Dithering and halftone are fundamentally different techniques, as they approach the same problem from the opposite ends.

    • Dithering uses uniform-size dots (or pixels in case of digital dithering), and varies their position to simulate more shades with fewer base colours.
    • Halftone uses uniformly-spaced dots, and varies their size to simulate the missing shades.

    That's the best I've ever heard it put.

    However, post #574601 makes me question uniform-size part of the dithering definition. The shading is made with strokes that vary their density and size (although there's some consistency in the spacing between parallel strokes), but it's still dithering.

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  • r0d3n7z

    Serlo said:
    However, post #574601 makes me question uniform-size part of the dithering definition. The shading is made with strokes that vary their density and size (although there's some consistency in the spacing between parallel strokes), but it's still dithering.

    The dithering tag in post #574601 refers not to the hatch shading strokes, but to the background.

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  • Serlo

    You have a better eye (or monitor) than I do. So the shading strokes don't count as dithering then?

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