Finding the last few unfilled regions
The picture looks finished and the counter says four regions remain. The leftovers are the smallest regions in the densest part of the image, and at fit-to-screen scale the display has already averaged them away.
The picture is finished. You can see that it is finished. The counter says four regions remain, and you have now spent longer hunting for them than you spent colouring the last two colours put together.
Why the leftovers are always the hard ones
It is not bad luck. The order in which regions get filled is roughly the order in which they are easy to see and easy to hit, so whatever survives to the end has been selected for being neither.
- They are the smallest regions in the picture, because the large ones were obvious and went early.
- They sit in the densest part of the pattern, where surrounding detail hides them.
- They are often slivers — long thin regions squeezed between two others, with a lot of boundary and almost no interior.
- They frequently belong to a colour that has only a handful of regions in the whole picture, so there is no cluster leading you towards them.
At fit-to-screen scale they are literally not there
This part is worth understanding properly, because it turns the problem from a failure of attention into a fact about optics.
When a detailed picture is fitted to a phone screen, one screen pixel is covering several pixels of the artwork. The display has to choose a single colour for that screen pixel, and what it shows is some average of everything underneath. A region three artwork pixels across, sitting between two filled neighbours, is averaged into them before your eye is involved at all. There is nothing left on the glass to notice.
Then there is your eye. Fine detail is only resolved in the fovea, a small central patch of the retina, and acuity falls off steeply within a couple of degrees of it. Looking at a whole picture at arm’s length gives you a sharp coin-sized area and a soft impression of everything else. Scanning the whole picture at once is not something your visual system can do — you are sampling it a patch at a time whether you intend to or not.
So failing to see the last regions is not carelessness. Some of them are not on the screen, and the ones that are sit outside the part of your vision that could resolve them.
What works
Look for the highlight, not the number
With a colour selected, most apps mark its unfilled regions conspicuously — a solid tint, a checkerboard, a pulsing outline. A marked region can remain visible at a scale where its printed number is long gone, because a highlight can be drawn with high contrast against its surroundings while a two-pixel digit cannot be drawn legibly at all. At low zoom you are hunting for a flicker of contrast, not for a shape you recognise.
If the highlight style is configurable, a moving or pulsing one is worth trying for this specific job. Peripheral vision is poor at detail and comparatively good at change, so something that blinks can catch you from the corner of your eye where something merely tinted will not.
Scan in quadrants rather than wandering
Divide the canvas into four and search one quarter at a time, zoomed in far enough to actually resolve small detail. Finish a quarter before moving on. Wandering feels faster and reliably re-covers the same ground while leaving one corner untouched, which is why the region you eventually find is so often somewhere you would have sworn you had already looked.
Use whatever next-region control exists
Many apps have an affordance that jumps the view to an unfilled region of the current colour. Where one exists this problem simply does not, and the honest advice is to stop being a completionist about finding them by eye. It is worth looking along the toolbar for it before starting a dense picture rather than after twenty minutes of searching.
Zoom into the dense areas on principle
Rather than scanning everywhere, go straight to the places small regions live: the centre of a mandala, the crossing points of a lattice, the seam where two large areas meet and slivers accumulate, and the outer border where a pattern is compressed to fit. Checking four likely places properly beats checking the whole canvas badly.
When it stops being worth it
If you have been looking for five minutes, leave it. The picture is not damaged by four unfilled regions, and it will still be there tomorrow, when you will probably find them in ten seconds because you are coming to the canvas fresh instead of with the search pattern you have already worn into it. A completion counter is a convenience for locating work, not a score that needs settling tonight.
Frequently asked questions
Why can I not see the last regions even though the counter says they exist?
At fit-to-screen scale a region a few artwork pixels wide is averaged into its neighbours by the display before you ever look at it, so there is nothing on the glass to see. Zooming in restores it. This is a limit of the view, not of your attention.
Does zooming out help me find them?
Zooming out helps you find the highlight, because a marked cluster is visible as contrast at almost any scale. It does not help you find the region itself. The usual sequence is to spot the highlight from a wide view, then zoom into that area to work.
Is there a faster way than scanning the picture myself?
If the app has a control that jumps to the next unfilled region of the current colour, use it — the search is exactly what it exists to remove. Otherwise, searching quadrant by quadrant is much more reliable than wandering, because wandering leaves gaps you cannot detect.
Do a few unfilled regions spoil the finished picture?
Visually, almost never — if you cannot find them at normal viewing distance, nobody looking at the picture will see them either. The only thing they spoil is a completion counter, and that is a tool for finding work rather than a verdict on the result.
Try it on a real canvas
Numbrush is colour by number for adults: mandalas, rose windows and geometric pattern work, twelve colours a picture, a magnifier for the tight spots, and a wrong tap that costs you nothing. Free, offline, no ads and no account.