Why your traced photo looks blotchy — and how to fix it

Flat patches where there should be a smooth gradient, hard bands across a sky, mottled skin. Five settings cause it, and each has a different fix.

What is actually happening

Vector shapes have one flat colour each. A photograph does not: a cheek, a sky, a wall lit from one side are continuous gradients, thousands of subtly different values shading into one another. Turning that into vector art means deciding where one flat colour stops and the next begins — and every one of those decisions is a visible boundary.

Blotchiness is what you see when those boundaries land in the wrong places or there are too few of them. The tracer is not malfunctioning; it is showing you the cost of the settings it was given. Every fix below is a way of spending more shapes in the areas that need them.

Cause 1: too few tones (the usual one)

Color Quantization sets how many distinct colours the whole image is reduced to. At 4 or 8 tones, a sunset that spans two hundred subtly different oranges gets four, and you get concentric bands. This is the cause perhaps three times out of four.

Fix: raise it. For photographs start at 24 tones and go up. Faces, skies, and water — the three subjects that show banding worst — often want 32 to 48. Go one step at a time and regenerate; the improvement is obvious when you have found the right level, and beyond it you are only adding file size.

Cause 2: Polygon Fill Size set too large

This controls how aggressively small regions are merged into their neighbours. It is there to suppress noise, but it works by erasing small shapes, and in a gradient the transition between two tones is made of small shapes. Set it too high and those get swallowed, so instead of a gentle handover you get one flat field butting straight against another — a hard edge across an open sky.

Fix: lower it. On photographs, small values are usually right; reach for a large value only when you are actively fighting speckle. If raising it fixes noise but introduces banding, you have gone past the balance point — go back a step and raise Color Quantization instead.

Cause 3: the wrong Source Type

Flat Graphic mode snaps to flat colour and traces clean, simplified edges. On a logo that is exactly right. On a photograph it is a guarantee of blotchiness — you are explicitly asking for hard-edged flat regions on an image made entirely of soft ones.

Fix: for any photograph, painting, or illustration, use Photo / Art — Organic Contours. It is built to keep organic contour and texture through the transitions. This single setting fixes more blotchy results than anything else on the page.

Cause 4: noise and compression in the source

The tracer faithfully reproduces what it is given. A high-ISO photo carries sensor noise; a heavily compressed JPG carries 8 × 8 blocking. Both mean neighbouring pixels that should be identical are not, and the tracer duly builds separate shapes for them — which reads as mottling, especially in shadows and flat walls.

Fix: denoise before you trace. A light blur or noise reduction pass in any photo editor, then vectorize the cleaned file. It feels backwards to throw away detail before tracing, but the detail you are removing is not detail — it is noise, and it costs you thousands of junk shapes. If you cannot pre-process, raise Polygon Fill Size a little and accept the trade against Cause 2.

Cause 5: Quality Level too low

Quality Level is the master dial: it sets the internal working resolution, the number of colours, and the fill size together. At low levels the engine works on a downscaled copy, so fine gradient transitions are gone before tracing even begins.

Fix: raise it to 6–8 for photographic work. If generation becomes slow, that is the honest cost — a smooth photographic trace is simply more shapes than a logo trace. Reduce the source image's dimensions rather than the Quality Level if you need the speed back.

Also check: Detail Distribution

If the middle of your image looks good and the outer parts look coarse, that is not a bug — it is Center Detail doing its job, keeping the middle sharp and deliberately simplifying the edges. It is a genuinely good choice for portraits and any image with a clear subject, because it puts the shapes where the eye goes. If you want even treatment across the frame — a landscape, a pattern, an architectural shot — switch to Overall Detail.

Starting points by subject

The trade-off you cannot escape

Every fix for blotchiness adds shapes, and shapes are the file. A smooth 48-tone portrait at Quality 8 might be tens of thousands of polygons and a multi-megabyte SVG that makes a browser work. That is not a flaw in the settings; it is the arithmetic of representing a continuous-tone image with discrete flat regions. Decide what the file is for: a print master can afford the shapes, a web graphic usually cannot.

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