How many colours a chart needs

The slider goes up to thirty. That is not a recommendation: past a certain point every extra colour adds another skein to buy and another thread to switch, and almost nothing to the likeness.

Colour count is the one builder setting that changes both how the chart looks and how long the piece takes. Every colour in the legend is a skein to buy and another thread to switch to mid-row. So the question is not which count is most accurate — the maximum is. The question is where accuracy stops being worth the work.

What actually disappears

Below is one picture put through the builder four times. Only the colour slider changed; width, fabric and everything else are identical. These are not mock-ups: the charts are built by the same code that processes your photo, and they were generated while this page was being assembled.

Source image

Colours requested4

Colours requested8

Colours requested12

Colours requested20

At four colours the flower is still recognisable, but the centre is gone entirely — the gold ring and the dark middle have merged into the petals, because no separate shade was left for them. The background has split into two flat blocks with a visible seam: where the original has a smooth gradient, the chart has to pick one or the other.

At eight the dark centre comes back, though the gold around it does not. At twelve both the gold ring and the soft shading on the petals return. Between twelve and twenty, though, you have to hunt for the difference: a slightly smoother background, a slightly softer shadow on one petal. Eight more skeins for that.

This threshold moves with size. The larger the chart, the more cells fall across each transition, and the more the extra shades earn their place. On a chart 200 stitches wide twenty colours make sense; on the 40 stitches shown here they simply vanish.

So how many

• A first project — 8 to 12. Enough for a recognisable image, and the shopping stays a single trip.
• A portrait, or anything with soft shadows — 12 to 18. Facial shadows are the first thing to break into flat patches, and here every shade still works.
• Graphic art, ornament, lettering — 4 to 8. There are no gradients to preserve, and extra colours only add noise.
• More than 20 — only on a large piece, from 150 stitches wide. On anything smaller you will not see them, and you will stitch twice as long.

A practical way to choose: set the slider to 10, then add two at a time and watch the chart. The moment two more colours change nothing you can see is your ceiling. It differs for every picture, which is exactly why there is no single right number.

Why you sometimes get fewer than you asked for

The builder is not obliged to return exactly the number on the slider. It looks for groups of similar shades inside the picture itself, and if the picture is simpler than the request, there is nothing to fill the extra groups with. On a flat logo there will be no difference at all between ten and twenty. That is fine: the legend always shows the real number of threads, not the one you asked for.

The reverse happens too. If you placed a colour by hand and then reduced the palette, that thread stays in the legend as its own row — you chose it deliberately, and the builder has no business removing it.

The numbers and charts on this page are computed by the same code as the builder.

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