What is ISO?

What is ISO

The acronym ISO refers to International Standards Organization. This gives us absolutely no clues as to how it is relevant in photography. The ISO setting on a camera controls how responsive the camera’s sensor is to light. This is universal across all brands and types of cameras. ISO settings are the same on phone cameras and on all types of film for film cameras.

The term ISO has been around since the early film photography days, but why is it still relevant in the digital age? ISO is one of the most important camera settings in digital photography

Along with shutter speed and aperture controls, different ISO values have an effect on the exposure of a photograph. So when you want to capture images that are well exposed, the ISO must be managed effectively.

Making Good Use of ISO in Photography

The ISO setting is one control on a camera that allows you to control how bright or dark a photo is. The other two are aperture and shutter speed. A high ISO setting means the sensor is more responsive to light. A low ISO setting has the opposite effect. So, in bright light, use a low ISO setting. When the light is low, use a high ISO rating. 

Choosing the right ISO for the lighting conditions will help you maintain a fast shutter speed when you need to. The camera’s base ISO setting is probably low and will not be suitable for all lighting conditions. Using a lower ISO means you will often need to use a slower shutter speed. 

This is one of the key advantages of digital photography. You can choose a low ISO or a high ISO for each image you make. With film cameras, you do not have this option. You are stuck with the base ISO of the film speed until you change the film.

ISO Setting in Film

In terms of film sensitivity, ISO is used as a rating system to tell you how responsive the film is to light. This is the film speed.  The lower the ISO setting (i.e 50), the more time the film needs to be exposed. The faster the ISO film speed, the less light is required to take a picture.

This is the same in digital photography, you just have more flexibility to adjust ISO settings and can do so as often as you like. Using a film camera you must expose the whole roll of film at the same ISO settings. If you make ISO adjustments part way through a film it will throw out the exposure when the film is developed it will not be correct.

What are the ISO Values?

Each camera will vary, but the ISO value can range from ISO 50 to a much higher maximum ISO. Here are the ISO values you’ll discover in many digital cameras: ISO 100, ISO 200, ISO 400, ISO 800, ISO 1600, ISO 3200, and ISO 6400.

Notice how each number is doubled as the ISO values increase. When you double the ISO speed, your exposure value adjusts by double. So, if your native ISO setting is 100 and you change the ISO value to 200, your exposure becomes brighter. 

You can adjust your aperture and shutter speed to compensate for this. In digital photography, cameras usually allow you to manage the ISO settings in one-third of a stop increments. Aperture and shutter speed settings also adjust in one-third increments.

ISO and Noise

Increasing the ISO to a high value affects your exposure. It can help you set a faster shutter speed. But it does have its consequences. Every time you shift from a low ISO value, it creates something called digital noise. This is not the same as film grain.

Digital noise will show up as tiny spots or bright pixels on your photos. They are more noticeable in darker areas of the image and are less noticeable when you use a low ISO.

Digital noise is affected by the size of the pixels in the camera sensor. Larger pixels will result in less digital noise. This is why DSLRs and mirrorless cameras do a fantastic job at higher ISO values compared to compact cameras.

With this in mind, it’s a good idea to maintain a low ISO value and adjust the aperture or shutter speed first. Sometimes, however, lighting conditions are poor and you will have to compromise image noise for brightness. But with most modern digital cameras there is not so much noise as in older cameras.

Luckily, many cameras nowadays do an amazing job of managing sensitivity to light to maintain image quality. You can be more flexible in your exposure triangle settings. You can choose a fast shutter speed when you need to without such a risk of getting noise from your digital sensor in your images.

What is the Best ISO?

When you want to keep a fast shutter speed, in many situations it is not possible to produce an image with low ISO sensitivity. Such situations include those where there is low light and no tripod. Or where the motion is very quick such as in sports photography you will risk motion blur. In this scenario, you’ll want to use a high ISO. A low ISO is not suitable.

Man photographing outside on a sunny day looking at ISO settings in the DSLR camera screen.

On a sunny afternoon however, you won’t have any problems with light. You can use a low ISO. Between a sunny day outside to nighttime photography, you will have to experiment with low ISO and high ISO values. You need to find the right balance between exposure and image noise to find the best ISO. Here is a quick guideline of common ISO values depending on the lighting situation:

  1. Bright, sunny day outside: Use a Lower ISO, 100 or 200 or your base ISO
  2. Cloudy days, indoors, or window light portraits: ISO 400
  3. Indoor photography without flash: ISO 800
  4. Reserved for very low light conditions: A high ISO of 3200 or higher

Suggestions for ISO Settings in Various Scenarios:

  • Dusk: ISO 200 to 400
  • Stars: ISO 800 to 1600
  • Sunsets/Sunrises: ISO 200
  • Evening Parties: ISO 800
  • Stormy Weather: ISO 400

Since you want the sharpest photos possible the ISO is a setting to keep an eye on. Remember that the higher you set the ISO the lower light your camera can handle. At higher ISO settings the sensitivity to light increases. When you want a brighter image and avoid motion blur, you need the camera’s sensitivity to be higher.

Modern cameras are great, but sometimes it is still necessary to use a tripod and a longer shutter speed. This can help you get more depth of field when using ambient light or flash and avoid camera shake. When there is not enough light, the challenges of setting the exposure triangle are greater to capture a correct exposure.

Film ISO vs Digital ISO

If you are using a film camera there is a much better chance that you are already familiar with the ISO number. When you choose your film you select the ISO number. Digital cameras are not so constrained by a roll of film having one set ISO sensitivity. You can change the digital sensors’ ISO sensitivity for proper exposure of every frame.

In film photography, when the ISO is too high, photos tend to appear grainy.  Grain is often mistaken for being the same as noise, but it is not. How ISO affects the look of the film is different from the high ISO effect on digital sensors.

How does ISO affect a digital image? In low light, the higher the ISO, the greater the risk of digital noise than at the lowest ISO setting. With a low ISO number, you see less noise and smaller grain than at high ISO settings in a proper exposure.

What is Native ISO?

Native ISO, is a crucial camera setting that will help you in producing the highest image quality. This is the baseline setting your camera is automatically set to for the best image quality and detail. 

At this setting, your camera’s sensitivity is optimized. This particular ISO is best whether you are using a full-frame camera or a crop sensor. Most cameras have this setting as the lowest available. Understanding ISO helps you capture light and maintain the best image quality.

What is Auto ISO?

Auto ISO allows photographers to manage their noise balance while taking photos. Turning on Auto ISO is never a good idea if you’re prioritizing Shutter Speed or Aperture mode. Allowing the camera to increase or decrease the ISO based on the current exposure settings take more creative control from you. 

Getting a good grasp on understanding ISO and how it functions will help you make better choices about setting up your camera. This, in turn, will produce good quality photos. This is why it is important to control your ISO manually.

How to Adjust the ISO Settings?

There are many ways to adjust the ISO depending on the type of camera you have. The following are the most common ways:

  • Get your camera out of Auto Mode. Including Auto ISO. Manually control the exposure triangle for the best results.
  • You can change the ISO value from the menu.
  • On more advanced or professional cameras, there is usually a dedicated ISO button. Press down on the ISO button while turning on the dial to change the ISO values. If you don’t see an ISO button, you may be able to customize it. Check your user manual for more information. 
  • Some cameras will also feature wheels where you can quickly change the ISO.

ISO Camera Setting Tips

  1. Do you hate that flashy look of photos indoors? Turn the flash off, lower your aperture and raise your ISO. You shouldn’t need a flash.
  2. Want to tell a story with your photo? Open your aperture all the way (lots of people refer to this as wide open) and blur out some elements of the photo. This is a shallow depth of field.
  3. Photographing sports? Set shutter speed faster and your subject suddenly becomes sharp! Use a higher ISO to help you maintain a fast shutter speed.
  4. It helps to take three or four pictures, each with different settings, so you can get a feel for how each setting will change your photo.

Debunking the ISO Myths

There are many misconceptions about ISO and how it works. Let’s take a quick look at the most common myths:

  1. ISO is related to exposure.
    Interestingly, ISO is not part of exposure. Whereas aperture and shutter speed physically capture more light into the camera sensor, ISO doesn’t do that. Instead, ISO brightens or darkens a photo based on the captured image. This is why many photographers don’t consider ISO part of the exposure triangle.
  2. ISO is the sensor sensitivity.
    This is probably the most common myth about ISO, and it’s actually false. ISO doesn’t reduce or increase the amount of sensitivity in your camera sensor. In fact, your digital camera only has a single sensitivity. ISO simply brightens your photo based on the current exposure. It maps how bright or dark the photo will be based on the ISO values.
man taking photo of sunset mountains with ISO 200.


Learning to control ISO helps to get your images correctly exposed. It helps us control the other two parameters of the exposure (aperture and shutter speed) which all work together to create a proper exposure. 

  • The higher the ISO, the more responsive the film or digital sensor is to light.
  • ISO speed affects aperture and shutter speed choices.
  • The higher the ISO, the more grainy or noisy pictures may appear.

Knowing how these parameters work together will help you grow as a photographer. This understanding helps develop your creative vision. Especially when you are photographing in various light conditions. With enough practice, you’ll be turning the dials and adjusting your ISO settings without thinking twice.

We hope this information was useful and that you’re ready to start controlling your ISO! Let us know your thoughts, comments, and experiences below about ISO.

ISO Explained


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