How to Pronounce ISO in Photography

You’ve probably heard ISO pronounced as a word and as an acronym. You may even use ISO both ways, too, because both are popular. So, which way is the correct way?

In this article, we’re going to briefly discuss what ISO is, its history, and how to pronounce it correctly.

What Is ISO?

First and foremost, ISO is a member of the exposure triangle (aperture, shutter speed, and ISO). All three of these camera settings work together to determine how bright or how dark an image will be, along with other qualities like depth of field and sharpness.

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ISO controls the amount of light that’s picked up by the camera’s sensor. In practice, ISO can be dialed in for both technical and aesthetic purposes. Generally speaking, a lower ISO results in less noise or grain, and a higher ISO will give you more noise or grain.

Related: What Is an ISO File and What Does ISO Mean?

Analog Photography (Film)

In analog photography, ISO is the film speed and its sensitivity to light. The lower the ISO value, the less sensitive the camera will be to light. For example, if you have a roll of film with an ISO of 100, it’s best suited for shooting subjects that are relatively bright. If you’re shooting darker subjects, then you might want to use an ISO 1600 or 3200 film roll.

Digital Photography

For digital photography, the same concept applies. But instead of using film emulsion for exposure, a signal-to-noise ratio is calculated and processed in the electronics. All this means is that there’s a direct relationship between the amount of light (the signal) and the amount of noise.

A Brief History of the Term ISO

ISO stands for the International Organization for Standardization, an independent non-governmental organization that sets the international standards for various types of measurements. ISO in photography doesn’t refer directly to this organization, however.

Ever since the two film systems DIN and ASA were combined in 1974, we’ve been referring to it as ISO internationally from that point on.

People are often confused about whether ISO is a word or an acronym. The International Organization of Standardization clears up the confusion in their About Us section on how to pronounce their name:

Because ‘International Organization for Standardization’ would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), our founders decided to give it the short form ISO. ISO is derived from the Greek ‘isos’, meaning equal. Whatever the country, whatever the language, we are always ISO.

The Correct Pronunciation of ISO

As far as the photography community is concerned, the case is closed. ISO is not an acronym but a word, so it’s not pronounced “eye-es-oh”. The correct pronunciation is “eye-so“, with alternate Greek pronunciations cast aside.

Now You Know How to Pronounce ISO

Now we know how to say ISO. But if a photographer pronounces it as an acronym or otherwise, we still know what’s being discussed. Let’s get back to what it’s all about; taking great pictures!