What Does ISO Stand For?

As a cinematographer or aspiring filmmaker, you’ve probably started to learn a lot about various camera components and their relationship to exposure. For example, you may know that aperture, ISO, and shutter speed are all part of the exposure triangle and that they work together to influence the amount of exposure that occurs when capturing a shot or scene. It’s true, cinematographers learn an awful lot in their early filmmaking careers, especially when it comes to exposure, but what does ISO stand for, exactly?

What is ISO?

ISO represents an acronym that stands for International Organization for Standardization. Informally, ISO may be used to describe the International Standards Organization. So what is the ISO, exactly?

The International Organization for Standardization is a working body that provides standardization of various productions or results so that consumers and those utilizing the products are able to compare them across a unique rating system. 

In cinematography, ISO uses the ASA film rating system to define sensitivity of a camera sensor. Using the ISO rating, cinematographers and photographers are able to understand, with a simple look at the ISO measurement, how sensitive a camera sensor is.

Unfortunately, ISO ratings are not measured in absolute standards. So, although one would expect an ISO rating on one camera to have the same sensitivity of another camera with the same ISO rating, the ISO ratings are not absolute measurements.

Thus, the same rating from one camera to the next will not necessarily equal the same sensitivity level. In fact, the same ISO rating for a particular profile of your camera may have a different sensitivity factor then that same ISO rating when used in another profile that you select.

Essentially, it’s not apples to apples, and although an inch is always an inch, and ISO 50 is not always the same as the next ISO 50.

How Is ISO Measured?

ISOs are measured in stops, similar to aperture which is measured in f-stops. ISO stops represent values that are typically doubled increments, for example:

• ISO 50
•  
• ISO 100
•  
• ISO 200
•  
• ISO 400
•  
• ISO 800
•  
• ISO 1600
•  
• ISO 3200

And so on…

Understanding Base ISO

When you ask, “What does ISO stand for?” another common question that frequently comes up is what is base ISO or, as some reference it, what is native ISO? 

Essentially, when describing Base ISO, or Native ISO, camera companies are providing you with insight into the absolute best quality performance standard for the camera sensor. Camera sensors are all made up of pixels, similar to television monitors and computer screens. 

Each pixel is responsible for the production of what is known as maximum dynamic range and color, representing the pixel’s best performance. This occurs at one, and only one, ISO which is reflected as Base ISO or Native ISO for the camera. 

This is the degree chosen by engineers that work at the camera companies and is based on individual characteristics of the camera sensor, basic color science, and individual goals of the camera.

What Happens When ISO is Adjusted?

Now that you have the answer to the question, “What does ISO stand for?” Let’s take a look at how things change when you adjust ISO. Changing the ISO will cause changes in dynamic range as well as color performance which can be seen in your images.

Remember what we said about Native ISO? Essentially, ISO shouldn’t be changed. 

YES, your camera may allow you to change your ISO. Yes you may have even taken shots with different ISOs and maybe the outcome wasn’t too dramatic — or maybe you didn’t notice any major changes at all when you adjusted the ISO at all. So what happens when ISO is adjusted?

The color performance of your film may appear “off” and the dynamic range of your film. Basically, it’s never a good idea to change the ISO setting on your camera as this may cause a ton of struggle for your editing team in post production as they attempt to color match and improve all final footage. 

Just keep the ISO set to base ISO and you’ll get the best quality form your equipment!