What Is ISO In Photography?

ISO is one of the primary camera settings that you use to control the exposure of your image. It is represented by a number typically anywhere from 50 to as high as 32,000 or more.

Like other camera settings it is represented in ‘stops’ and each full stop up is double the lower stop (ie. 100, 200, 400, etc.)

Understanding ISO in Photography

ISO is often referred to as the sensitivity of your camera’s sensor to light. This isn’t technically correct.

More accurately, ISO is the level to which your camera amplifies the light hitting the sensor (much like a music amp will amplify sound).

A higher ISO number means a brighter image, allowing you to capture images in low-light conditions without using a flash. On the other hand, a lower ISO number means less light amplification, resulting in darker images.

As you experiment with different ISO settings, you’ll notice it affects the overall quality of your images as well. For instance:

  • Low ISO (e.g., ISO 100 or 200): At lower ISO settings, your images will have finer grain and less noise, providing a higher image quality. However, you may require more light or slower shutter speeds to achieve the desired exposure.
  • High ISO (e.g., ISO 800, 1600, or higher): With higher ISO settings, your camera will capture images in darker situations, but the trade-off is increased noise and grain, reducing the overall image quality.

It’s important to find the right balance between ISO, shutter speed, and aperture to produce the desired outcome for your photographs.

The image below was shot at night with an ISO of 100 but I had to put the camera on a tripod and use a 6-second shutter speed to get enough light to expose the image properly.

ISO and Light

Generally, it’s best to use the lowest ISO possible that still allows you to achieve the correct exposure for a given scene. This helps you maintain the image quality without sacrificing the desired exposure.

Here are some tips for adjusting ISO in different scenarios:

  • Bright outdoor scenes: You should typically use a low ISO value (e.g., ISO 100 or 200) to minimize noise and maximize image quality.
  • Indoor or low-light conditions: Increase the ISO value (e.g., ISO 800 or 1600) to enhance the camera’s sensitivity to light, but be aware of the trade-off in increased noise and grain.
  • Action or fast-moving subjects: You might need to raise the ISO to capture images without motion blur, especially when using faster shutter speeds to freeze the action if there isn’t a lot of light.

As you continue to practice your photography skills, you’ll become more comfortable adjusting your camera’s ISO settings to achieve the desired image quality and exposure in various lighting conditions.

Understanding ISO can help you capture better images in various lighting conditions.

In bright environments, using a lower ISO setting can prevent your photos from becoming overexposed. Conversely, in darker situations, increasing your ISO can help you capture images without sacrificing shutter speed or aperture.

Noise and ISO

Raising your ISO comes with a trade-off: It can introduce noise or grain into your images, reducing their overall quality.

That’s why it is essential to find the right balance between an adequately exposed photo and minimized noise. Here are some general guidelines for ISO selection:

  • Bright sunlight: Use ISO 100 or 200 for clear, sharp images with minimal noise.
  • Overcast or indoor natural light: ISO 400 to 800 works well for these conditions, providing more light sensitivity with minimal noise.
  • Low-light or nighttime photography: Use ISO 1600 or higher to capture enough light without relying solely on slow shutter speeds or wide apertures.

Let’s take a look at a cropped-in section of that first image at various ISO settings. I used a Nikon Zfc for these shots and an aperture of f/8.

ISO 100

ISO 400

ISO 6400

ISO 25,600

ISO 51,200

Ultimately, the ideal ISO setting will depend on your specific circumstances, camera, and personal preferences. Don’t be afraid to experiment with various ISO settings to achieve the best results! And remember to always use your camera’s ISO feature responsibly to get the most out of your photography.

Effects of ISO on Image Quality

When working with ISO in photography, it’s important to understand how it can affect your image quality. In this section, we will discuss the effects of high and low ISO settings.

High ISO

Using a high ISO setting can help you capture images in low-light environments without the need for a flash or a longer exposure time. However, there are some drawbacks to consider:

  • Graininess: High ISO settings tend to produce more digital noise which can result in a grainy or ‘noisy’ appearance in your photographs.
  • Loss of detail: Along with the noise, high ISO settings can cause a reduction in the sharpness and overall detail within an image, making it less visually appealing.


In contrast, low ISO settings provide a smoother, cleaner image quality, with less digital noise and more detail. However, they also come with their own set of challenges:

  • Longer exposure times: To compensate for the lower sensitivity, slow shutter speeds or wider apertures are required, which can make it difficult to capture fast-moving subjects or shoot handheld without camera shake.
  • Limited low-light performance: Low ISO settings can make it tough to capture well-exposed images in dim conditions without resorting to additional lighting or a tripod.

Finding the right balance of ISO is key to achieving the image quality you desire. Consider your shooting environment and the subjects you will be capturing to determine the optimal ISO sensitivity for your photographic needs.

How to Choose the Right ISO

A good rule to follow is to start at your base ISO, and then work through your settings with increasing ISO as the last resort if you can’t get a bright enough exposure any other way.

What is a Base ISO?

When selecting the appropriate ISO, start by identifying your camera’s base ISO, which is the lowest ISO setting that delivers the highest image quality.

Most cameras have a base ISO of 100 or 200 but some may be as low as 50 or 64. For optimal results, it’s best to use this setting whenever possible. Keep in mind that using a higher ISO may sacrifice some image quality to achieve faster shutter speeds.

Available Light and Shooting Conditions

Consider the lighting conditions when determining your ISO. In scenarios with ample natural light, you can generally use lower ISO settings – such as the base ISO – to capture well-exposed photographs.

On the other hand, if you’re in a low-light environment, increasing your ISO may be necessary to properly expose your images without resorting to a tripod or flash.

To better adjust your ISO to lighting conditions, consider the following:

  • Daylight: Use the base ISO for outdoor shots during bright, sunny days.
  • Overcast: Slightly raise the ISO, perhaps to 400, for cloudy or overcast conditions.
  • Indoors: Depending on available natural or artificial light, you may need to increase the ISO to 800 or higher.
  • Low Light: Set the ISO between 1600 and 6400 for dimly lit scenes or night photography.

Moving Subjects

When you’re photographing moving subjects or aiming to freeze motion, a higher ISO becomes more crucial. This allows you to maintain faster shutter speeds, which subsequently reduces motion blur. When determining the appropriate ISO for moving subjects, take into account the following factors:

  • Subject Speed: Faster-moving subjects might require higher ISO settings to effectively freeze movement.
  • Lighting: As mentioned earlier, consider the available light in the scene to determine how much you should increase the ISO. If it’s bright enough, then you don’t need a high ISO to use faster shutter speeds.
  • Desired Depth of Field: If you need a larger depth of field, keep your aperture smaller and increase your ISO accordingly.

For the image above, I needed to use an ISO of 400 even in the middle of the day so I could get a fast enough shutter speed to freeze the action.

Experiment and practice with different ISO settings, considering the factors above, to refine your ability to choose the right ISO for your photography.

ISO and Camera Types

Different camera types have different ISO capabilities, which can impact their performance in various lighting conditions.

DSLR and mirrorless cameras, for example, usually have a broader ISO range than point-and-shoot cameras or smartphone cameras (generally due to larger and/or more advanced sensors). This wider range allows you greater flexibility when shooting in different environments and ensures optimal image quality.

Understanding your camera’s ISO capabilities will help you take advantage of its full potential.

Most cameras have an automatic ISO setting, which adjusts the ISO based on the available light in your scene. This can be very helpful for those new to photography or when shooting in conditions where the lighting changes frequently.

However, if you want to take full control of your camera’s settings, it’s important to manually adjust the ISO according to your needs.

Keep in mind that cameras with larger sensors typically perform better at higher ISO levels. This is because they can collect more light, thus reducing the amount of noise in the image. Some high-end cameras are specifically designed to produce excellent image quality even at very high ISO settings, such as ISO 12,800 or 25,600.

When selecting a camera, consider its ISO capabilities and how they align with your photography needs. For instance:

  • If you primarily shoot indoors or in low light conditions, look for a camera with a wide ISO range and strong performance at higher ISO levels.
  • If your photography mostly involves bright, well-lit environments, a camera with a smaller ISO range might be sufficient.
  • If you want to shoot fast action, such as sports or wildlife, a camera that performs well at higher ISO levels will enable you to use faster shutter speeds, which can help freeze motion and prevent blur.

Knowing the ISO performance of a camera is just one factor in making informed decisions when selecting a camera and optimizing your photography in various lighting conditions.

ISO and Post-Processing

In post-processing, you can use noise reduction techniques to minimize the appearance of this noise. Software like Adobe Lightroom and Photoshop have noise-reduction tools that allow you to reduce the graininess in your images without sacrificing too much detail.

Another aspect of ISO in post-processing is adjusting exposure. If you find that your images are underexposed due to a low ISO setting, you can increase the exposure in post-processing to brighten your images.

Sometimes, increasing the exposure in post-processing will give you a slightly less noisy image than shooting at a higher ISO to begin with. You’ll have to experiment with your camera to see what works best.

Post-processing enables you to fine-tune the ISO-related aspects of your images. By managing digital noise, exposure, and sharpness, you can enhance your photographs and achieve the desired result.

Reducing Noise In Your Images

You can use editors like Lightroom or Photoshop to reduce the noise in your images. But the best one I’ve tested recently is the Topaz Photo AI software. It does a lot more than noise removal too. I highly recommend trying it out.

Frequently Asked Questions About ISO

Is ISO “sensor sensitivity”?

No, ISO is not sensor “sensitivity,” despite the multitude of content out there referring to ISO as changing the “sensitivity” of the sensor, that is not what is really happening. Your camera sensor’s sensitivity to the light is constant and does not change. Increasing the ISO is like digitally amplifying the light that is captured by the sensor. This is one reason why you begin to see distortion as you increase the ISO.

Is ISO part of exposure?

ISO is not technically part of exposure, although many photographers tend to look at it as part of the settings that will adjust exposure. In fact, only the aperture and shutter speed actually affect the amount of light hitting the sensor and thus the exposure. But ISO can increase the brightness of the light that is exposed to the sensor.

What is the best ISO setting for landscape photography?

The best ISO setting for landscape photography is the base ISO of your camera (typically 64 or 100) because that will give you the cleanest and sharpest image. However, that may vary depending on what type of landscape photography you are shooting and whether you are using a tripod.

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