What is ISO in Photography? Understand when to use ISO

ISO in photography determines the sensitivity to light for the image sensor. It is the last option we can rely on when both aperture and shutter speed are set up. Getting a perfect shot requires an appropriate balance of aperture, shutter speed, and ISO. ISO gives the photographer a boost and allows him/her to increase exposure without compromising aperture & shutter speed. Let’s take a dig right into what ISO is in photography, and how it can aid you.

The Name ISO & ISO in Film Cameras

ISO stands for the International Organization of Standardization. ISO is actually an organization that sets that standard for different kinds of measurements. In the context of film cameras, ISO refers to the sensitivity to light of a film. Unlike digital sensors which can use different ISO range, film cameras could only choose a single ISO after they shoot the entire film.

Role of ISO in Photography?

ISO can be your friend and enemy. I had multiple moments when I relied on ISO, and there are moments I hated it. It took me some time to make peace with this setting. While understanding ISO, it is important to learn how it works. Any hybrid camera supports ISO from 100 to 12400 (minimum). Setting ISO at 100 gives you the lowest sensitivity to light. Now, when you increase it to 200, the sensor boosts the light sensitivity by increasing the gain.

Shutter speed and aperture control the amount of light that enters the sensor whereas the ISO controls how the light is perceived at the sensor end. This is how ISO is able to control light sensitivity in a camera. Also, the amplification of voltage applied to the sensor in effect increases the noise. We will discuss that next.

ISO in Photography: The Foe

Understanding your machine’s limits is more important than knowing its pros. Likewise, it is important to know what ISO can cost you when you rely on it too much. If you already have a camera and started playing with ISO you would have seen it.

Increasing ISO in turn increases the gain in the sensor. This in effect amplifies the noise, along with the signal. Noise does not collaborate with ISO, noise is intrinsic to the sensor. However, increasing sensitivity in effect adds more noise which makes a noisy image, or the digital equivalent of grain. Hence, relying too much on ISO can add noise to the image.

Understanding ISO in Photography - Introduction of noise due to high ISO

Every camera has its own moderate range of ISO that produces sharp and well-lit images. The photographer has to find the right ISO range for his/her camera.

Given that, there are newer hybrid models in the market that perform extraordinarily in low light conditions, for example: Sony a7S III.

ISO in Photography: The Friend

Now let’s see where ISO in photography will be your companion:

Sports & Animal Photography

Shutter speed is the most crucial part while taking a moment involving action. Increasing the shutter speed to capture more light may create a blurry picture of the action. The aperture is crucial to set the depth of field to the image, and also exposure. In such a moment, when you cannot tweak the other two options, but you need a bit of light, it is then the ISO comes into action. ISO provides a significant amount of boost in such a case.

Low-light Shooting

Low light shooting conditions are the most feared situations by a photographer. It is interesting that low light photography can also give excellent photos with silhouettes, color painting, motion trails, etc. ISO is definitely helpful at these moments. While shooting in low light, you may run into a situation where your aperture is wide open and you don’t want to lower your shutter speed. ISO would come in handy at such scenarios, you can raise it to the desired level to get the perfect exposure. No matter how large the ISO range your camera supports, bear in mind that after a certain point, it will introduce noise. If low light shooting is your thing, consider going for a camera with a larger pixel size. For example, Sony a7S III full frame mirrorless camera that excels in low light shooting. Even at extreme ISO settings, this camera delivers amazing and incomparable results.

Significance of ISO in Indoors or Wedding Photography

Shooting at a wedding or other indoor programs, the photographer has to make sure that the subjects stay focused on the image. Shutter speed is the key here, lowering the shutter speed to gain more light can create blurred images when there are fast motions. ISO steps up for you at this moment. Once you cover the lighting, you can lock your shutter speed and tweak ISO for better light. Keep in mind that a higher aperture during an indoor shoot can give you refreshing images.


Raising the ISO in extremes sometimes becomes a necessity and noise issues just become inevitable. To counter such issues, we recommend using third-party software like Adobe Lightroom.

Learn the weaknesses of your machine, embrace it, and then you can make wonders with your camera.

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Adarsh R

A blend of a photographer, a movie lover, and now a writer.