Ever wonder how those funky aperture numbers ended up on your lens barrel? Or who chose those odd f-numbers that run in the seemingly arbitrary 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 sequence? And why does the biggest number refer to the smallest lens-hole?

Now, video sketching supremo Dylan Bennett is back to explain f-stops to you. Grab a beverage, sit back and enjoy 15 minutes of easy-to-follow explanation. With drawings!

You don’t need to know any of this to take photos — other than that each f-stop lets in exactly half or double the amount of light as the one next to it up or down the line. But if you have any interest in how things work, along with some basic high school math, you’ll probably enjoy this video as much as I did.

Bonus: If you have trouble remembering the sequence of numbers, there’s a little trick (one which I realized by reverse engineering the numbers themselves, which are burned into my photographers brain). If you can remember the first two numbers, you’re good to go. Just double them, and interlace the results. Thus, 1, 2, 4, 8, 16, 32 interleaves with 1.4, 2.8, 5.6, 11, 22 to gives you the sequence above. And that’s why math is so neat (apart from the slightly fudged 5.6 to 11 part).