From an everyday question to the next discovery.
QR Code correction percentages are approximate measures relative to all codewords. They do not guarantee that a certain fraction of the image area can be erased; location markers and reading conditions matter too.
In editorial order. You can move to another field at any time.
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The “up to about 30%” quoted for error recovery does not refer to the area of the paper. Separate the information encoded in the black-and-white pattern from the markers that help a reader find it.
The paper has twice the area, but its height and width are only about 1.414 times as large. Move between a size chart, a folded sheet, and a copier's display to discover the mathematics hidden in A-series paper.
The spaces between short and long signals follow rules of their own. Place International Morse code’s intervals of 1, 3, and 7 units on the same timeline, and the information carried by silence becomes visible.
A screen adds light; ink on paper absorbs some of it. Move the same photograph between the two, and the differences involve white, black, the range of reproducible colors, and even the lighting in the room.
Energy per task and total electricity demand answer different questions. Read the IEA’s 2026 outlook through a small model of efficiency, use and the boundaries around a number.
Content Credentials can record how an image was made. Verifying that record and verifying an event are different jobs. Four fictional cases make the boundary visible.