What does ISO stand for in photography?

Sooner or later, we all ask: what does ISO stand for in photography? Even when you know what ISO does, you might not know what it actually means! 

If you're still wondering what is ISO in photography, this helpful guide might help you. But in terms of its meaning, the answer might surprise you… 

ISO doesn't actually stand for anything! 

What does ISO stand for in photography?

ISO isn't an abbreviation. It refers to the International Organization for Standardization, a body that creates thousands of agreed standards for a huge range of products. However, it isn't an acronym for it – because, as the Organization itself states, that would be different depending on the language.

"Because 'International Organization for Standardization' would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), its founders opted for the short form 'ISO'," states the Organization on its website.

"The story goes that ISO is derived from the Greek word 'isos', meaning equal. Whatever the country, whatever the language, we are always ISO." 

ISO, then, refers to the International Organization for Standardization but doesn't stand for it. And, if it stands for anything, it's the Greek work for equal. 

What does it do? 

In terms of photography, ISO is simply a set of numbers that describes a scale of sensitivity to light. This was established in the era of analog photography, and related to the "speed" of film; the higher the ISO of the film, the more sensitive to light and the "faster" it was – enabling you to employ faster shutter speeds.

Today, of course, most cameras have replaced film with a digital image sensor. But ISO still describes light sensitivity, and acts as the master brightness control for your camera. The more you increase the ISO, the brighter your exposure will be.

So, what does ISO stand for in photography? Strictly speaking, the answer is nothing!

You might be interested in the best film cameras and the best camera film. If you're interested in the best ISO performance, take a look at the best low-light cameras.