Name: Camera Basics - ISO
Uploaded: 2026-03-14T09:03:32.000Z
Duration: 4 min 38 s
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While shutter speed and aperture control the amount of light physically hitting the sensor, ISO controls the amount of light the camera needs and is a representation of the sensitivity of the image sensor.

As the ISO increases, the light it takes to expose the image decreases.

For example, doubling the ISO from, say, 400 to 800 results in the camera needing only half as much light for the same exposure.

This is the main reason such high ISO values are used in indoors, especially at sporting events, and

Needing a fast shutter speed to freeze action, and

often with limited light available, photographers pump up the ISO as far as they are comfortable doing.

However, increasing your ISO doesn't come without drawbacks.

Microphones gather sound waves from a source, just like cameras gather light rays from the environment and each turn them into electrical signals, which are outputted as either a sound file for a microphone or an image for a camera.

Now, what happens if you're trying to record something very faint, like a whisper?

You increase the sensitivity of the microphone.

However, besides the whisper being louder, background noise is amplified as well, and

you may even hear the hum of the microphone's electronics.

So similarly, increasing the ISO of a camera increases its sensitivity to everything, revealing any lighting artifacts as well as any electrical grain in the system.

In the world of photography, higher ISO values don't just produce more noise, they also reduce the color accuracy and dynamic range.

So you should use the lowest ISO value possible at all times.

The lowest ISO value of your camera is considered the base ISO, a term that you may come across in the future.

This ISO produces the best image quality and lowest amount of noise, but

as stated earlier, low ISO values require lots of ambient light to properly expose the scene.

It's also worth mentioning that not all cameras will have the same ISO profile.

The ISO performance of your camera largely depends on the size of the photo sites in your camera.

When you press the shutter button of your camera, the curtain in front of the image sensor slides up, exposing the photosites to ambient light.

The photosites gather photons that enter through the lens, and

once the exposure is over, the curtain slides over the sensor and the camera assesses the amount of photons that were gathered, converting the number into an image.

Larger sensor cameras allow for larger photo sites, which can gather more photons, so full frame cameras have an advantage over crop sensor cameras.

Also, lower megapixel counts mean that each photosite is allowed to take up more space on the sensor, increasing photo site size.

However, older lower megapixel sensors are not better for low light shooting, as advances in microlens design and the silicon itself have made modern sensors more efficient.

Remember that in every case you should try to decrease your ISO as much as possible to retain image quality, but

sometimes you may be forced to use higher ISOs.

Low ISOs are particularly useful in outdoor photography, where the sun will provide lots of light for your camera, allowing you to more freely use faster shutter speeds and smaller apertures.

ISO for indoor photography is largely situational.

Depending on how well lit the area is, you may want to use higher ISO values.

Remember that if your subject is not moving, you can use a slower shutter speed or if you're okay with a shallower depth of field, use a larger aperture.

Night photography, whether it be a moonlit photo shoot or astrophotography, will inevitably require high ISO values.

This is where you need to experiment with your camera to find out how far you can push it without serious drawbacks.

ISO, while appearing to be a complicated subject, is actually very simple.

By exploring your camera's ISO profile and realizing when to use high and low ISOs, with an understanding of the principles of image noise and sensitivity, you will be able to directly improve the quality of your photos and be more comfortable with your camera.

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