How to use Auto ISO in Photography

Michael • updated November 5, 2022 • 3 min read

How to use Auto ISO in Photography

ISO Automatik is a powerful tool that is available in many camera models and does excellent work in rapidly changing lighting conditions.

Some people adore it, while others despise it. And the majority have no idea how it works or is unfamiliar with the function.

The reality is that Auto-ISO behaves very differently in different camera modes. While she is extremely useful in many situations, it can have a negative impact on others.


What is ISO?

ISO is the rating of the camera sensor’s sensitivity to light. A lower ISO value, such as 50 or 100, means that the sensor requires slower shutter speeds and/or larger apertures to properly expose an image.

Higher ISO values such as 1600 or 3200, on the other hand, require faster shutter speeds and/or smaller apertures to properly expose an image.

Of course, we are also aware that image quality decreases at high ISO values due to ISO noise. But then, would you rather have a little noise than blurry photos? As you can see, the ISO value is very important.

Read also How to Take Sharp Photos.

Why ISO values?

In order for an image to be perfectly exposed, three parameters must be matched. This is called the exposure triangle:

Shutter speedcontrols how long light falls on the image sensor. The aperture controls how much light enters the camera through the size of the opening.

The ISO value determines whether and how the received signals must be amplified.

What is Auto ISO?

When the ISO automatic is enabled, you can freely select the aperture and shutter speed in M mode, and the camera adjusts the ISO value to ensure proper exposure.

Because of the high image noise in older camera generations, this automatic mode should be used with caution. However, today’s low-noise camera models, it provides significant advantages and maximum flexibility.

Always choose your aperture and shutter speed with the brightest shooting situation in mind. For example, if you are photographing in a dark room and in direct sunlight, the camera may significantly increase the ISO value for indoor shots but not lower it below the minimum ISO value for outdoor shots.

If the shutter speed is too slow here, the images will inevitably be overexposed. Depending on the camera model, the ISO automatic range can be limited to avoid exceedingly high ISO values.

Unless you combine auto ISO with aperture priority or shutter priority, this can result in underexposed images. This method allows you to use both automatic modes without the risk of a noisy or blurry image.

Read more about Camera Mode Settings Explained.

When to use ISO automatic mode?

  • People
  • Animal, wildlife photography
  • Street photography, available light (without a tripod)
  • Concert and theater photography
  • Indoor photography without a tripod
  • Wedding photography
  • Photographing at festivals without flash
  • Sports photography
  • Museums, etc

When not to use ISO automatic mode?

  • Studio shots
  • Night shots
  • Water flowing
  • Situations with consistent lighting conditions

When using a tripod, select the lowest ISO setting possible. ISO automatic is useless in this situation.

Quicklinks to camera manufacturer Auto ISO setting:

Frequently asked questions

Should I leave the ISO on Auto?

Is It Necessary to Use Auto ISO? You absolutely should! As you may have guessed, Auto ISO is a fantastic feature that comes in handy when the light changes quickly or you don’t have time to adjust your settings in a hurry.

What exactly does Auto ISO do?

The Auto ISO feature instructs the camera to adjust the exposure based on changing lighting conditions. As the light in the image dims, the shutter speed decreases to allow more light in and ensure proper exposure. When it reaches the “minimum” shutter speed, the ISO rises to maintain proper exposure.

Should I use Auto ISO when shooting in aperture priority?

As long as you’ve set your maximum ISO and minimum shutter speed, your camera can adjust the ISO and shutter speed to ensure that the image isn’t too bright or too dark. When you meet the minimum shutter speed you’ve set, the camera raises the ISO.

What exactly is auto ISO sensitivity?

Auto ISO sensitivity control allows the camera to automatically adjust ISO sensitivity if optimal exposure cannot be accomplished at the value chosen by the user. Maximum ISO sensitivity: Select the maximum ISO sensitivity to prevent the auto ISO sensitivity control from selecting a value that is too high.

Is Auto ISO mode used by professional photographers?

Many professional photographers use their cameras in semi-automatic modes such as Aperture Priority or Shutter Priority, which share some of the responsibility for exposure with the camera’s computer-controlled exposure.

Interested in more photography Read our article in outdoor portrait photography.

Is it possible to use Auto ISO with Flash?

Auto ISO is compatible with TTL flash, which plainly changes its power level to maintain the same metered TTL exposure as ISO changes. The camera can be set to Manual mode, but the flash remains TTL.


What do you think about how to use Auto ISO? Let us know in the comments.

By Furoore team member Michael
Furoore Team is here to assist you in capturing the most significant moments in your life. To create exciting photographs, discover photography guides, find unique photo ideas, and limitless image inspiration.


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