What is ISO?

What is ISO

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.

You may have heard of the Exposure Triangle, which consists of Shutter Speed, Aperture, and ISO. These three work together harmoniously to create a perfectly balanced and exposed image.

What is ISO in Photography?

ISO stands for International Organization for Standardization, and it is a lot easier to understand than its name. ISO is a setting that allows you to control how bright or dark a photo is, and it is a standard telling you how sensitive your film/digital sensor is to light. The higher the ISO value is, the brighter your photos will look. Adjusting the ISO is a quick and easy way to brighten up your images when you’re shooting in dark environments. This allows a lot more flexibility when you’re working within the Exposure Triangle (aperture, shutter speed, and ISO).

ISO Setting in Film

In the photographic world, ISO is most commonly referred to as a film rating system. Think film photography, not the movies. In terms of film, ISO is used as a rating system to tell you how sensitive the film is to light, or how fast the film is.  The lower the ISO number (i.e 50), the more time the film needs to be exposed. The faster the ISO film speed, less light is required to take a picture.

What are the ISO Values?

Each camera will vary, but the ISO values can range from ISO 100 to ISO 6400. Here are the most common 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 photos will also double in brightness which means the values are relative to each other.

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ISO and Noise

Increasing the ISO to a high value can instantly brighten up your photos, but it does have its consequences. Every time you dial up the ISO value, it creates something called image noise. Film photographers will call it image grain, but the term noise is more common among digital photographers. Image noise will show up as tiny dots or “grain” on your photos and are more noticeable in darker areas of the image.

One thing to note is that digital noise is affected by the size of the pixels used in the camera sensor. Larger pixels will result in less digital noise, which is why DSLRs do a fantastic job at higher ISO values compared to a compact camera. DSLRs have a much larger sensor and pixel count.

With this in mind, it’s a good idea to keep the ISO value as low as you can and adjust the aperture or shutter speed first. Sometimes, however, lighting conditions are poor and you will have to compromise image noise for brightness. It’s all part of the joy in photography and experimentation, isn’t it?

Luckily, many cameras nowadays do an amazing job of keeping the image quality high even at a higher ISO value. Although they’re at a higher price tag, these professional cameras allow you to shoot at very high ISO without compromising quality.

What is the Best ISO?

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. In this scenario, you’ll want to use a high ISO.

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 and can therefore lower your ISO to a much lower number. In between a sunny day outside to night time photography, you will have to experiment with the ISO values 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: ISO 100 or 200
  2. Cloudy days, indoors, or window light portraits: ISO 400
  3. Indoor photography without flash: ISO 800
  4. Reserved for very low light conditions: ISO 1600

Suggestions for ISO in Various Scenarios:

  • Fireworks: ISO 100 (do not change)
  • 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, however that higher ISO will also increase the amount of visible noise or graininess also. You want to find a balance between how dark it is and how much noise you can get away with in your photos without it ruining the shots. 

Also be sure to have a tripod available when you are going to be in low light settings to be sure to minimize the movement involved that would possibly make it grainier. You will want to do everything you can to make it sharp, even when you have to raise the ISO.

Film ISO vs Digital ISO

If you are using a film camera there is a much better chance that you are already familiar with ISO. When you choose your film you select the ISO. Digital photographers are not so constrained by a roll of film having one set ISO sensitivity, and can change the ISO sensitivity rather easily.

That isn’t to say digital cameras can escape the adverse effects of shooting with higher ISO. In film, when the ISO is too high, photos tend to appear grainy.  The same is true with Digital Cameras instead of being called grainy it’s called noise. The higher the ISO, the the more noisy digital photos appear. Whether your using film, or a digital camera, ISO speed affects the aperture and shutter speed combinations you can use.

What is Native ISO?

Native ISO, is a crucial camera setting that will help you in producing the highest image quality. When you adjust your camera to Native ISO, this is the baseline setting your camera is automatically set to for the best image quality and detail. When you go under or above the Native ISO your camera sensor will be more sensitive to the fluctuating light. This is why it’s optimal to keep your camera at Native ISO as much as possible.

What is Auto ISO?

Several years back, many cameras started introducing Auto ISO setting which allowed photographers to manage their noise balance during shooting. Turning on Auto ISO is 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. Certain cameras will even allow you to set a parameter for the Auto ISO sensitivity so it doesn’t go over the limit you set it to.

Getting a good grasp on ISO and how it functions will help you make better choices about setting up your camera, which in turn, will produce good quality shots.

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. This will allow you to adjust the ISO in Shutter-Priority, Aperture-Priority, or Manual Mode.
  • Most beginner DSLRs will require you to enter the Menu mode to access the ISO. You can change the ISO value from the menu.
  • For more advanced or professional cameras, there is usually a dedicated ISO button on the camera itself. 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.

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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? Turn your aperture all the way down (lots of people refer to this as shooting wide open) and blur out some element of the photo, ie, a baby with a big sibling blurry but in the background.
  3. Shooting sports? Set shutter speed faster and your subject suddenly becomes sharp!
  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 just brightens or darkens a photo based on the captured image. This is why many photographers don’t consider ISO part of exposure.

  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 is a fast way 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 balanced image. 

  • Higher the ISO, the more sensitive the film/sensor is to light.
  • ISO speed affects allowed aperture and shutter speed combinations.
  • Higher the ISO, the more grainy or noisy pictures may appear.

Knowing how these parameters work together and their connection to each other will help you grow as a photographer and develop your creative vision when you are out shooting with various light conditions. With enough practice, you’ll be turning the dials and adjusting your ISO settings naturally 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.

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