What is ISO in photography?

Mastering the Basics: What is ISO in Photography? A Beginner's Guide

ISO is essential to getting great images in all lighting conditions. I adjust my ISO settings depending on whether I'm photographing a serene landscape on a tripod or navigating the busy streets of Toronto and New York with my camera in hand.

ISO stands for International Organization for Standardization, the body that created the numbers we use to measure a camera's sensitivity to light. In simple terms, ISO refers to the sensitivity of your camera's image sensor to light. The ISO setting affects the brightness and noise in your images, so it's a fundamental part of digital photography.

What is ISO?

ISO is one of the three parts of the exposure triangle in photography, along with aperture and shutter speed. The ISO setting controls how sensitive your camera is to light and how much light your sensor needs to get the correct exposure. A higher ISO makes your camera more sensitive to light, which is beneficial in low-light conditions. Conversely, a lower ISO is best suited for bright, well-lit scenes to achieve the best image quality.

In digital photography, ISO settings are the first thing photographers adjust when faced with challenging lighting. Adjusting the ISO gives photographers control over exposure, allowing them to shoot in a wide range of environments, from bright daylight to nighttime.

ISO Settings

ISO settings are expressed as numbers, such as ISO 100, 200, 400, and so on. These numbers represent the camera sensor's sensitivity to light. Lower ISO numbers (e.g., ISO 100) indicate lower sensitivity, which is suitable for bright conditions. In contrast, higher ISO numbers (e.g., ISO 1600) are used in darker conditions where more sensitivity is needed to achieve a well-exposed image. 

ISO Setting: Get it Right

The ISO setting on your camera is crucial for achieving the correct exposure in all lighting conditions. To achieve the best image quality, start with the lowest ISO setting possible, typically 100 or 200. Then, increase the ISO as the light fades, or a faster shutter speed is required. The goal is to find the balance between light sensitivity and noise.

My primary goal is to achieve the best quality for every shot, primarily since I aim to produce high-quality wall art prints. A higher ISO setting is advantageous in low-light conditions but can introduce more digital noise. However, modern digital cameras have significantly improved their high ISO capabilities, allowing you to shoot at ISO 3200, 6400, or even higher with minimal noise, especially when a tripod isn't an option and you must avoid camera shake. A higher ISO setting is beneficial in low-light conditions, but it also introduces increased digital noise. However, modern digital cameras have significantly improved their handling of high ISO settings, allowing you to shoot at ISO 3200, 6400, or even higher with minimal noise. This flexibility is valuable when you can't use a tripod and need to avoid camera shake.

ISO and Camera Controls

ISO works in conjunction with other factors to form the exposure triangle, along with your aperture and shutter speed. Adjusting your ISO affects the other two settings; therefore, understanding ISO is essential for achieving the correct exposure.

• ISO and Shutter Speed: When you increase ISO, you can use a faster shutter speed to freeze motion, which is suitable for action photography. Using a lower ISO, you can use a slower shutter speed to create motion blur, achieving an artistic effect.
• ISO and Aperture: Adjusting ISO also affects your aperture. For example, when shooting in low light and needing a smaller aperture for depth of field, increasing the ISO may be required to achieve the correct exposure.

Understanding how ISO works in conjunction with aperture and shutter speed is crucial for achieving well-exposed images in any lighting condition. By mastering these three camera settings, you can reach the correct exposure whether you're shooting indoors or outdoors in low-light conditions.

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ISO in Different Photography Genres

Different types of photography require different approaches to ISO settings. Here's how to use ISO in various genres:

• Portrait Photography: Use a low ISO (e.g., ISO 100) to achieve clean, noise-free images, especially in controlled lighting conditions. Portrait photographers prioritize image quality and detail, so a lower ISO is ideal.
• Landscape Photography: Landscape photographers typically use low ISO settings to achieve high image quality and detail. However, increasing the ISO may be necessary in darker conditions to avoid camera shake during prolonged exposure. A higher ISO can also help you achieve a faster shutter speed, which is essential for freezing motion in dynamic scenes.
• Sports and Action Photography: This genre requires a higher ISO to freeze fast-moving subjects, especially in less-than-ideal lighting. High ISO helps you capture sharp, detailed action shots, combined with a fast shutter speed. In sports photography, the balance between ISO, shutter speed, and aperture is critical in capturing those moments.

I shoot various genres of photographs on my worldwide travels and use different ISO settings for different circumstances. Remember that increasing the ISO introduces digital noise, a grainy texture that can ruin the quality of your image. On a tripod, I almost always use the camera's native ISO. In the case of the Sony a7R V, which I currently use, that is 100 ISO. But even that can vary. If I shoot a landscape with grass and tree branches blowing, I will increase the ISO to achieve sharpness throughout the image. Also, Adobe Lightroom's AI denoise and tools like Topaz DeNoise AI can significantly reduce noise while maintaining excellent image quality.

ISO Myths and Misconceptions

ISO needs to be more precise, especially regarding its role in exposure. A common myth is that ISO controls the amount of light entering the camera. In reality, ISO doesn't change the light; it amplifies the camera's sensors' response to the light it receives, making an image appear brighter and introducing noise.

Another myth is that high ISO always ruins image quality. While it's true that increasing the ISO introduces noise, modern digital cameras have improved dramatically in handling high ISO settings, allowing you to shoot at ISO 1600, 3200, or even higher with minimal noise. Over the years, I have used almost every camera brand - from Canon and Leica to Nikon and Hasselblad, and I kept switching to find the camera with the best high ISO quality. I primarily switched to Sony's mirrorless cameras, starting with the Sony a7R III and now using the current version. I love the high ISO quality. I know that Canon and Nikon have also made significant strides in their sensors, but I have yet to use them to comment on which is better. Regardless of the camera manufacturer, the improvements in modern digital camera sensors mean you can use higher ISO settings without compromising image quality, especially in low-light conditions.

ISO and Image Quality

Image quality is one of the most important things to consider when adjusting your ISO. Lower ISO means better image quality, more detail, and less digital noise in any situation. For the highest image quality, I use the lowest ISO possible in well-lit scenes. However, there are times when a higher ISO is necessary to achieve the correct exposure, especially in low-light conditions or when a faster shutter speed is required to freeze motion.

Using auto ISO can be helpful in dynamic environments where lighting changes rapidly. Auto ISO allows your camera to adjust the ISO automatically, ensuring you always capture a well-exposed image without needing to manually adjust the settings.

ISO and Dynamic Range

Now, the effects of increasing ISO are less well understood by general photographers. High ISO increases noise and reduces the camera's Dynamic Range.'

Dynamic range refers to the range of light intensities your camera can capture, from the darkest shadows to the brightest highlights. For example, consider a scene where you are on a street where the front of a building is bathed in sunlight, but next to the building is a laneway that is in shadow. When you expose the brightly lit building facade, the laneway will become dark, even black. When your camera can no longer record detail in the dark section, it goes black, and there is no way to recover that. So, your dynamic range is the camera's ability to record data from the brightest part of your picture to the darkest part. The greater the range, the higher quality you will get without having to bracket your exposure and take multiple photos to capture all ranges of light in your scene.

ISO plays a significant role in your camera's dynamic range.  

ISO plays a significant role in your camera's dynamic range. At lower ISO settings, your camera will have a higher dynamic range and more detail in both shadows and highlights. As you increase the ISO, the dynamic range decreases, resulting in a loss of detail in both the brightest and darkest areas of your image.

Understanding the relationship between ISO and dynamic range is crucial for photographers seeking the highest image quality. Generally, when shooting in bright conditions with high contrast, it's often best to use a lower ISO, which maximizes the camera's dynamic range, allowing you to capture as much detail as possible in both highlights and shadows.

ISO and Digital Noise

Digital noise is the grainy texture in your images, particularly when shooting at high ISO settings. Noise is more visible in the shadow areas of your photo, which reduces the overall image quality. However, noise isn't always bad; in some cases, it can add texture or mood to an image, much like film grain.

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Modern digital cameras have significantly reduced noise, allowing you to use higher ISO settings without sacrificing image quality. Post-processing software can further reduce noise and enhance the final image.

ISO Speed and Your Photos

ISO speed refers to the rate at which your camera's sensor can capture light. A higher ISO setting means the sensor is more sensitive, allowing you to shoot in low light without needing a slower shutter speed or a wider aperture. This is useful when you need to avoid camera shake or motion blur.

However, remember that a higher ISO can also introduce more digital noise to your images. The key is to find the balance between ISO and image quality, depending on your shooting situation.

ISO Tips in Photography

Balancing ISO, aperture, and shutter speed is crucial for achieving the best images. Here are some tips:

• Balance ISO with Other Settings: Consider how ISO affects your camera's aperture and shutter speed to get correct exposure without sacrificing image quality.
• Monitor Image Quality: As you increase ISO, check the noise in your images. Adjust ISO, aperture, or shutter speed to maintain the desired image quality.
• Use Auto ISO When Needed: If you're in a dynamic environment with rapidly changing light, use Auto ISO. This feature enables your camera to automatically adjust the ISO, ensuring your images are well-exposed without requiring manual adjustments.

• Experiment with ISO: Try different ISO settings to see how they affect your pictures. This will provide you with a better understanding of how ISO works in conjunction with other camera settings and how to utilize it creatively in various situations.
• Monitor Dynamic Range: Remember, a higher ISO can reduce your camera's dynamic range, causing it to lose detail in both highlights and shadows. In high-contrast scenes, use the lowest ISO setting to capture the most dynamic range and retain all the details.

ISO Setting: Tips for Different Situations

When choosing the proper ISO, the environment and type of photography you're doing are important factors to consider. Here are some tips for ISO in different situations:

• Bright Daylight: In well-lit conditions, such as sunny days, I use low ISO settings, like ISO 100 or 200, to achieve the best image quality. This minimizes noise, making your images sharp and detailed.

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• Low Light and Night: When shooting in low light or at night, you may need to increase ISO to 1600 or higher to get the correct exposure. However, be aware of the noise and consider noise reduction in post-processing. This is where you should experiment and learn about your camera, as well as how much noise you can tolerate. In the early days, I could keep raising the ISO and 'get the shot' - I felt a sense of freedom, and it was great. However, when I got home, I discovered that the images were too noisy to be usable; I then looked for great shots. Now, I keep my ISO below 1,600 on my Sony a7R V. It's Unnecessary because going higher produces poor images. Still, I know from experience that I want superb photos in print, and a resolution of 1,600 or lower gives me that result.

• Action and Sports: You need a fast shutter speed to freeze the action for moving subjects. This often requires a higher ISO, especially in not-so-good lighting conditions. Balancing ISO with shutter speed and aperture is crucial for capturing sharp and well-exposed action shots. For example, when shooting wildlife in Africa, I will increase my shutter speed to 1/1200 or even 1/5000 for birds in flight. So, even in bright conditions, my ISO could rise to 1600. But I get the shot I am after - that is the constant balance and tradeoff you must consider.
• Portrait: In portrait photography, especially when shooting in controlled lighting conditions, such as a studio setting, I always aim for a low ISO to achieve smooth skin tones and minimize noise. ISO 100 or 200 is ideal, but if the lighting is dim, you are shooting in natural light; for example, you might need to raise the ISO slightly to avoid a slow shutter speed that can introduce blur. When I shoot street portraits, I often use ISO 800 or 1200.
• Landscape: Landscapes are often shot with a low ISO to capture detail across the entire image, especially when using a narrow aperture to achieve a deep depth of field. However, you should use the ISO in low light conditions to avoid camera shake during prolonged exposure. Here, the tradeoff is between shutter speed and ISO. Using a sturdy tripod, I could increase my exposure time to 30 seconds or even a few minutes, while keeping my ISO at the optimum setting of 100.

Conclusion

Mastering ISO in photography is a crucial skill that can significantly enhance your ability to capture stunning images in any lighting condition. By understanding how ISO, shutter speed, and aperture work together and knowing when to adjust the ISO, you can enhance your photos without sacrificing image quality. Whether you're shooting in bright daylight, low light, or action situations, knowing how to use ISO effectively will give you the control to produce pro-level images.

Remember, practice and experimentation are the keys to using ISO effectively.  

Feel free to experiment with different ISOs in various conditions to see how they affect your images. The more you understand how ISO works in conjunction with other camera settings, the better you'll be able to capture the shot, regardless of the situation.

If you want to read more photography tips and tricks, check out my other photo mastery articles. In them, I discuss shutter speed, aperture, and best practices for different genres of photography.

If you’re interested in how visual storytelling goes beyond the camera settings, you might enjoy exploring how I approach deeper themes in my work—like the emotion tucked into rust and ruin in Worn Metal Forgotten Places, the impact of colour on mood and meaning in The Psychology of Colour in Wall Art, or even the surprising nuance behind a timeless tone in What Colour Is Sepia.

 Happy shooting!