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May 14, 2022

🌱 Why 4k ≠ 5k

And what Apple means when they say «Retina»

I’m pretty sure the Apple Studio Display is overpriced. Still, the discourse after its announcement has been plagued by people not quite understanding the difference between 4k and 5k on a 27-inch display. It’s just one kay difference — why can’t you just buy a 4k screen that’s cheaper, brighter and/or has a higher refresh rate? Why do some Apple fans crave this extra kay so much??

Marc Edwards, of Bjango, wrote an excellent piece on this, and I especially like the visual examples of 4k vs. 5k on macOS. ** As a maths teacher, I find this problem interesting, and here I will bring some light to this issue the way I would to a high school class.** Perhaps this makes it easier to understand why the issues Edwards highlight appear.

What’s in a kay?

To narrow things down, I’m mostly going to look at 27-inch screens with a 16:9 aspect ratio (so no super-wides here!). Let’s compare the three most normal resolutions at this size: 1440p, 4k and 5k.

Humans are notoriously bad at comparing large numbers. Every day, there’s a new tweet trying to help us understand the difference between a million and a billion, by reminding us that:

One million seconds ≈ 12 days
One billion seconds ≈ 31 years

So, it’s forgiven that people think 4k and 5k are pretty close. However, 5k resolution has _a lot _more pixels: