Why do the numbers disappear when you zoom out?
Nothing is broken. A digit needs a minimum height in pixels to be readable, and at fit-to-screen scale most regions cannot hold one. Drawing them anyway makes the picture harder to read, not easier.
You zoom out to see the whole picture and every number vanishes. Zoom back in and they reappear. The first assumption is that something has gone wrong — a rendering glitch, a setting you knocked with your thumb, a bug worth reporting.
It is deliberate, and the reasoning is worth knowing because it tells you what each zoom level is actually for.
A digit has a minimum size
Text is legible only above a certain height in device pixels. Somewhere below eight or nine pixels tall a digit stops being a shape you read and becomes a smudge you guess at; below four or five there is not enough there to guess with. This is not a matter of design taste, it is a consequence of how few dots are available to distinguish a three from an eight.
Now do the arithmetic for a fitted view. A detailed picture might be well over a thousand pixels along its long edge, displayed on a phone canvas a few hundred points wide. Every artwork pixel is getting a fraction of a screen pixel. A region twenty artwork pixels across — a perfectly ordinary small region — is a handful of screen pixels at that scale, with no room inside it for a readable digit. At fit scale most of the picture is in that situation, and only the largest regions could carry a label at all.
Drawing them anyway makes it worse
The tempting fix is to draw the numbers regardless and let the reader squint. That produces a specific and familiar failure: a wash of grey speckle across the artwork. Hundreds of unreadable marks do not convey their numbers, and they do obscure the shapes and boundaries that were perfectly visible underneath.
Part of this has an established name. Visual crowding is the effect where a target becomes unidentifiable because of clutter close beside it, even when the target on its own would be large enough to resolve. Packing tiny digits into every region of a dense pattern is a machine for manufacturing crowding: the labels interfere with each other and with the outlines, and the net information on screen goes down rather than up.
So hiding labels below a zoom threshold is not the app withholding something from you. Above the threshold they carry information; below it they carry noise.
Why there is often a cap on the count as well
Some apps stop drawing labels once there are more than a few hundred on screen, even at a zoom level where each one would individually be legible. There are two reasons.
- Text is expensive to draw. Each label has to be laid out, rasterised and composited, and doing that for a thousand of them on every frame while the canvas is being panned is the kind of load that turns smooth movement into stutter and warms the phone.
- A thousand labels at once is not usable anyway. Nobody reads a field of a thousand digits; you read the ones near where you are working. A cap costs you nothing you were using.
A related detail worth knowing: the anchor point matters as much as the size. A label should sit at the visual centre of its region — roughly the point furthest inside it — rather than at the centre of its bounding box, which for a crescent or a ring can fall outside the region entirely. Labels that appear to float in the wrong place are usually this, rather than an error in the artwork.
How to work at each zoom level
The practical consequence is that low zoom and high zoom are for different tasks, and trying to do the wrong one at the wrong scale is most of what makes the format feel awkward.
Zoomed out: navigate by highlight and shape
At full-picture view you are answering “where is the work”, not “which colour goes here”. Select a colour, let the highlight show you where its regions cluster, note the shape of the cluster, then zoom into it. Numbers are irrelevant to this task, because the app has already told you that every highlighted region takes the colour in your hand.
Zoomed in: confirm with the number
Once you are close, the number is a confirmation tool. It answers “is this really a seven, or did I misread the highlight”, which matters most in the fiddly places where two shades are close together. Use it as a check, not as a search index.
If you want numbers at a wider view
- Rotate the device, or move to a tablet. More physical pixels across the same artwork is the only real cure; everything else is a workaround.
- Zoom to a middle scale rather than all the way out. There is usually a band where the larger regions are labelled and a good part of the picture is still visible.
- Use a magnifier or press-and-hold preview if one exists, which gives a readable local view without disturbing the whole viewport.
- Check the settings for a label size or label density option. Not every app has one, but it costs nothing to look before you start a dense picture.
Frequently asked questions
Is it a bug that the numbers disappear when I zoom out?
No. Below a certain zoom level a digit would be a few pixels tall, which is not readable, and drawing hundreds of them anyway produces a grey speckle that hides the outlines underneath. Hiding them is a deliberate choice that leaves the picture more legible, not less.
Can I force the numbers to show at full-picture view?
Usually not, and where an app does offer it the result is generally worse rather than better. If you need labels across a wider area, the effective moves are rotating the device, moving to a larger screen, or settling at a middle zoom where the bigger regions are still labelled.
Why do some numbers still show when others do not?
Because legibility depends on region size, not on zoom alone. At a middle scale the large regions are wide enough to contain a readable digit and the small ones are not, so labels appear selectively. Zooming further in brings the smaller ones back in size order.
How do I know which colour a region takes if I cannot see its number?
Use the highlight instead. Selecting a colour marks every unfilled region that accepts it, and a highlight stays visible at scales where a digit cannot be drawn at all. Zoom in to read the number only when you want to confirm something specific.
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.