What is ISO in photography? Camera ISO Settings Guide

Changing your camera’s ISO settings affects the brightness of your photo. But how does it work and how do you choose the right ISO setting? Read on to learn all about ISO settings and take better pictures with this knowledge.

What does ISO mean? Origin of the term

ISO is the abbreviation of International Standards Organization. Camera ISO settings are approximations of the two previous systems as we know them today: DIN and ASA.

The DIN system, short for Deutsches Institut für Normung, was founded in 1934. Film speed was measured in “degrees” on a logarithmic scale. This system can be compared to today’s way of measuring decibels.

In 1943, the American Standards Association developed its own system under the name ASA. This standard is more similar to ISO as we know it today. The scale was linear, meaning that a film rated at 200 ASA was twice as sensitive as 100 ASA film, while the DIN standard required a hundredfold difference.

In 1979, film speed was standardized under the ISO system.

What is ISO? Analog and digital photography

ISO values ​​describe the sensitivity of a film or image sensor to light. Typical digital camera settings range from ISO 100 to ISO 6400. However, you can find values ​​as low as ISO 3 or as high as ISO 819200 on professional cameras. Higher ISO values ​​correspond to greater sensitivity to light.

In analog photography, films are coated with light-sensitive suspensions containing crystals or dye particles. Depending on the size of the crystals or particles, the film is more or less sensitive to light.

Image sensors have replaced film in digital photography. Technically, the image sensor has a fixed sensitivity to light. Again, you can change its sensitivity by adjusting the ISO settings. What actually changes is the gain of the sensor.

DSLR Camera Digital Sensor

Image sensors capture the incoming light as a kind of photon “rain”. Located behind the diaphragm, the image sensor consists of millions of discrete, light-sensitive units called photosites.

Each photocell consists of a photodiode and a charge amplifier that creates and amplifies an electrical charge when it hits a light-emitting diode. The electrical charge generated by each photocell reflects the intensity of light hitting the sensor at that location.

When you take a picture, each of these individual sections is briefly exposed to light from outside the camera body. During this brief period, each photosite reads the incoming light from its unique position on the image sensor and converts it into an electrical charge.

The camera’s image processor converts the sum of these electrical charges into what you’ll recognize as a photograph. The processor also performs various calculations such as exposure, white balance and image quality adjustments.

What does changing ISO settings do?

Low ISO and High ISO Underexposure Overexposure

When you increase the ISO setting of the image sensor, you increase its gain, that is, the amplification of the incoming signal. This increases the sensor’s sensitivity to light, but can also increase the level of noise or grain in your image.

While you can change the ISO setting to adjust the image sensor’s sensitivity to light, remember that your camera has a dynamic range of light levels that it can capture and reproduce at the same time.

Changing your ISO settings affects dynamic range, as lower ISO settings can reduce noise and increase an image’s dynamic range (the level of detail in bright and dark areas).

There are other important tools you should know when learning photography, such as why aperture is important and how to use aperture priority.

What is Native ISO?

ISO steps up on the Panasonic Lumix G DSLR

The ISO standard is measured in blocks divisible by 100, doubling up or down with each increment. In other words, ISO 200 becomes ISO 400 as opposed to ISO 300. Then ISO 400 becomes ISO 800 and so on.

A camera’s native ISO or base ISO is the lowest possible ISO value that the camera offers to the user. Because physical film could not be adjusted in this way, the term was not needed before digital cameras became the norm. Today, we use it to refer to the camera’s “ideal” ISO setting, although the best setting to use can vary depending on the light you’re shooting.

Other sources use the term to refer not only to the camera’s lowest possible ISO settings, but also to all possible camera ISO values. And this without manually expanding this range or using third-party programs.

For example, the Canon Rebel T2i can shoot between ISO 100 and 6400 right out of the box. With the Magic Flashlight installed, however, this range is extended to ISO 12800. However, you may damage your sensor.

When to use low ISO settings

Anything below ISO 100 is considered a low ISO setting. What are the benefits of shooting at low ISO?

The higher your ISO, the more likely your image will be affected by unwanted artifacts and digital grain. This is because increasing your ISO setting does not increase the amount of light entering the lens. When you increase the sensitivity, you are asking photo sites to extract “new” information from their surroundings when there is actually no additional information to take.

The resulting “guessing game” leads to many small errors that spoil the picture under the right conditions. If crystal clarity is your goal, shooting at the lowest possible ISO is your best bet.

It’s easy if the terms are clear and gentle. Those shooting in daylight in a studio or outdoors will have other ways to compensate for exposure if the subject calls for it. In this case, high-resolution photography has some disadvantages.

When to use high ISO settings


If you’re shooting at night or in low light, increasing the camera’s ISO sensitivity will help you gain ground. The trade-off between excellent clarity and adequate exposure can sometimes be worth the resulting digital noise.

If you’re up against a wall in terms of shutter speed and aperture diameter, ISO may be your only option. Those who enjoy low-exposure photography should invest in a camera that specializes in low-light performance.

The Sony Alpha series was a popular game changer in the field when it was released; Sony Alpha A7 can boast a maximum ISO value of 25600. Talk about some slack.

ISO value for each situation

As with all other fields of photography, there are no right or wrong answers, only pictures that go wrong. Make sure you’re on the safe side of the fence by making the most of your device’s native ISO sensitivity.

What if all else fails? The low-fi look is very fashionable. Cereal-loving hipsters everywhere will still love your work.

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