The Explanation LabAll 20 lessons

02 SEEING · How eyes read a picture

A property must mean something.

You will learn the seven ways a mark can change, and the one rule that makes them readable. It takes 3 minutes.

Watch for the jobs

The clip takes one dot and changes it seven ways. Then it shows a map where everything changes at once. Watch what happens when each change gets one job.

32 seconds · lesson 2 of 20 from the full video

The name for it

THE NAME FOR IT

Jacques Bertin's visual variables

Jacques Bertin, Sémiologie graphique · 1967

A mark can vary in position, size, shape, orientation, color, value and texture. Each one can carry a different piece of data.

The seven ways

POSITIONSIZESHAPEORIENTATIONCOLORVALUETEXTURE
One mark, changed seven ways. Each change can carry one piece of data.

That's the whole toolkit. Every chart, map and diagram is built from these seven. The trick isn't picking pretty ones. It's giving each one a job.

Without jobs

Here are 14 weather stations. Size, shape, color, value and orientation all change.

WIND AND RAIN, 14 WEATHER STATIONS · EXAMPLE DATA

Every property changes, and none of them means anything. What does a big purple square tell you?

You can see that the marks are different. You can't tell what the differences mean. That's confetti.

With one job each

Same 14 stations. Now each property carries exactly one thing.

WIND AND RAIN, 14 WEATHER STATIONS · EXAMPLE DATA

Position: where the station is. Orientation: wind direction. Size: wind speed. Color: blue means rain, gray means dry.

Read it now. Where's the strongest wind? Where is it raining? Which way is the wind blowing in the east? You can answer all three in a second, because each answer lives in one property.

TAKEAWAY

A visual property is useful
when it always means
the same thing.

Rules for giving out jobs

Rule Why
One property, one meaning If color means rain here, it can't mean region somewhere else.
Same meaning everywhere Keep the job for the whole page, report or product.
Match the property to the data Use size and position for amounts. Use color and shape for categories. Shape can't show "more."
Leave the rest alone A property with no job should stay constant. Random variety reads as data.

This site follows the rules too. Color has one job here: it tells you the family. Orange is SEEING, purple is SCREENS, blue is WORDS, green is STRUCTURE and pink is MINDS.

Ask your agent

Agents love to make charts colorful. This prompt makes them justify every property:

PROMPT
Before you draw this chart, write an encoding table:
one row for each visual property (position, size, shape, orientation, color, value, texture),
with the data field it shows, or "constant" if it shows nothing.
Rules: each property gets at most one field, and each field gets one property.
Use position or size for quantities. Use color or shape only for categories.
Any property marked "constant" must not vary in the chart.
Then draw the chart from the table.

Data and question the chart must answer:
[paste here]

What good output looks like: a short table first, with most rows marked "constant," and then a chart that matches it.

Sources