The meaning of ISO in photography: who cares?

This might be a somewhat controversial statement, but here it is: you don’t actually need to understand the true meaning of "ISO" to take great photos. That said, if you’ve spent any time on social media or YouTube, you’ve probably heard someone claim that ISO stands for “International Organization for Standardization.” Technically, that’s not correct. Yes, if you look at the first letter of each word in the English name of that organization, you do get I, S and O. But in French, the same body is called “Organisation internationale de normalisation”—which would abbreviate to OIN, not ISO.

So where does the term actually come from? It originates from the Greek word ísos (ἴσος), meaning “equal” or “the same.” This term appears in many English words as a prefix: isobar (equal pressure), isotropic (same physical properties in all directions), and isotope (same chemical element, same number of protons). Perhaps the most familiar example is the isosceles triangle, which has at least two sides of equal length and two equal angles.

In other words, ISO is not an acronym at all—even though many people treat it as one. The International Organization for Standardization chose the name ISO precisely because it was inspired by the Greek word isos, reflecting their mission to create standards that promote equality and consistency across the globe.

So next time you raise your ISO in low light, remember—you're not just turning up a number; you're invoking a principle of equivalence. Whether that means equal brightness or equal noise? That's up to you!