The hand
When the body
gets in the way.
On a phone your finger is the brush, and the body has limits a brush doesn't. A fingertip is the widest thing on the screen, right where the paint goes. It has no pressure a phone can read. It can't leave the glass to reach an edge. I wanted to work around each limit without asking you to learn anything: the app should correct itself, not ask.
A correction the app makes on its own, at the moment it is needed, beats a control you have to find.
The limits
- A finger hides what it touchesA pen shows its tip. A fingertip covers the colour coming off, the ridge it builds, whether the brush is running dry.
- Every known fix is for pointingLoupes, offset cursors and pushing content aside help you hit a target. None of them helps you watch a mark being made.
- A finger has no pressureThe phone cannot feel how hard you press, only how much of the fingertip is on the glass.
- Any offset leaves a strip you cannot reachIf the paint lands beyond the fingertip, the finger would have to leave the screen to paint the far edges.
- One hand holds, one thumb reachesControls far from the corners are hard to reach, and a near miss beside a button lands on the painting.
What I decided
The paint lands just above your fingertip, always the same distance
The paint goes down a fixed distance above your fingertip, a little to the left, so you see the mark as it's made, the way you see a pen's tip past the fingers holding it. I set the distance by the widest brush, and it never changes: not with the brush, not with where you are on the screen. "Above" is where gravity says, so if you turn the phone in your hand, the paint stays above your finger as you see it. An outline of the brush itself, its shape at its real width, shows the spot the moment you touch, before any paint.
Ruled out: the brush trailing behind the finger. It showed the paint, but paint that lags can't be placed.
Ruled out: aiming the paint along the finger, and bringing it home to the finger near the edges. It reached every edge, but the paint moved around the fingertip as you went. My note at the time: the drawing point "needs to be predictable above the finger, same distance".
Ruled out: twisting two fingers to aim it. It worked, and it was, as I put it, "too much work, hard to discover".
The bottom strip: zoom in to reach it
Because the paint is always above the finger (held upright), the last strip at the bottom of the screen, as tall as the nib's distance, can't be painted with the whole canvas showing. Zoom in and the strip covers less of the canvas; at full zoom it is a sliver. The very bottom of the screen belongs to iOS's swipe home anyway, and a stroke that starts there can leave the app.
Ruled out: swinging the paint toward the corner buttons. It reached most of the bottom of the screen and bent ordinary strokes. Far too aggressive.
Contact size stands in for pressure
From about 12 points of fingertip barely touching to about 34 pressed flat, the size of your touch sets how wide and how heavy the stroke is, as a brush spreads when pressed.
Controls where the thumb already is, forgiving of a near miss
Colours and brushes open from the two bottom corners, under the thumbs holding the phone; they open as you press and slide out, so one movement chooses. Each corner button catches touches a little beyond its edge, and a quick tap just beside one does not dab paint, while a stroke that starts there still paints.
Knowing what a brush will do before it touches
Sliding a finger across the brushes names each and says what it is for: broad strokes and clean edges, soft blending, long thin lines. The icons are drawn so no two brushes look alike.
Measured on real hands
How far the paint should sit from different fingers, and whether the contact range matches real touches, I'm measuring on the phone, not in a browser.
The full investigation into the covering finger What a phone can and cannot feel