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 photograph a serene landscape on a tripod or navigate 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 is how sensitive your camera's image sensor is to the 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 good in low light, and a lower ISO is best for bright, well-lit scenes to get the best image quality.

In digital photography, ISO settings are the first thing photographers adjust when faced with challenging lighting. Adjusting ISO gives photographers control over the exposure and allows them to shoot in all environments, from bright daylight to night.

ISO Settings

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

ISO Setting: Get it Right

The ISO setting on your camera is critical to getting the correct exposure in all lighting conditions. To get the best image quality, start with the lowest ISO possible, usually 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, especially since I aim to produce high-quality wall art prints. A higher ISO is advantageous in low light 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.

Getting the image look or effect is always the primary goal; determining the optimum setting to achieve that goal at the best quality is secondary. I want the optimum quality for every picture I take to create superb prints.

Higher ISO is good in low light but comes with increased digital noise. However, modern digital cameras have significantly improved their handling of high ISO so that you can shoot at ISO 3200, 6400, or even higher with minimal noise. This flexibility is valuable when you can't use a tripod and must avoid a camera shake.

ISO and Camera Controls

ISO works with other factors. It's connected to your aperture and shutter speed to form the exposure triangle. Adjusting your ISO affects the other two, so knowing ISO is essential to getting 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 for artistic effect.
• ISO and Aperture: Adjusting ISO also affects your aperture. For example, when you're shooting in low light and need a smaller aperture for depth of field, increasing the ISO might be required to get the correct exposure.

Knowing how ISO works with aperture and shutter speed is critical to getting well-exposed images in any lighting condition. By mastering these three camera settings, you can get the correct exposure whether you're shooting indoors or outdoors, bright or low light.

ISO in Different Photography Genres

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

• Portrait Photography: Use low ISO (e.g., ISO 100) to get clean, noise-free images, especially in controlled lighting. Portrait photographers prioritize image quality and detail, so a lower ISO is ideal.
• Landscape Photography: Landscape photographers usually use low ISO to get high image quality and detail. However, increasing the ISO might be necessary in darker conditions to avoid camera shaking during more prolonged exposure. Higher ISO can also help you get a faster shutter speed, essential in freezing motion in dynamic scenes.
• Sports and Action Photography: This genre requires higher ISO to freeze fast-moving subjects, especially in less-than-ideal lighting. High ISO helps you get sharp, detailed action shots combined with 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 your image. On a tripod, I almost always use the camera's native ISO - in the case of the Sony a7r V that I currently use, which 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 ISO introduces noise, modern digital cameras have improved dramatically in handling high ISO so that you can 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 switched primarily to Sony's mirrorless cameras - starting with the Sony a7r III and now to the current version V. 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 camera digital sensors mean you can use higher ISO without compromising image quality, especially in low light.

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. But there are times when a higher ISO is necessary to get the correct exposure, especially in low light or when you need a faster shutter speed to freeze motion.

Using auto ISO can be helpful in dynamic environments where lighting changes fast. Auto ISO allows your camera to adjust the ISO for you, so you always get a well-exposed image without modifying the settings manually.

ISO and Dynamic Range

Now, the effects of increasing ISO are less known to 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, your camera will have a higher dynamic range and more detail in shadows and highlights. As you increase the ISO, the dynamic range decreases, meaning you will lose detail in your image's brightest and darkest areas.

Knowing the relationship between ISO and dynamic range is essential for photographers who want the highest image quality. Generally, when shooting in bright conditions with high contrast, it's often best to use lower ISO, which maximizes the camera's dynamic range, giving you as much detail as possible in the highlights and shadows.

ISO and Digital Noise

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

Modern digital cameras have significantly reduced noise, so you can use higher ISO without sacrificing image quality. Post-processing software can help reduce noise even more and improve the final image.

ISO Speed and Your Photos

ISO speed refers to how fast your camera's sensor can capture light. Higher ISO means the sensor is more sensitive, so you can shoot in low light without needing a slower shutter speed or wider aperture. This is useful when you need to avoid camera shake or motion blur.

But remember, 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 with aperture and shutter speed is essential to get 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 fast-changing light, use auto ISO. This feature allows your camera to adjust the ISO for you so your images are well exposed without adjusting manually.
• Experiment with ISO: Try different ISO settings to see how they affect your pictures. This will give you a better understanding of how ISO works with other camera settings and how to use it creatively in different situations.
• Monitor Dynamic Range: Remember, a higher ISO can reduce your camera's dynamic range and cause it to lose detail in highlights and shadows. In high-contrast scenes, use the lowest ISO to get the most dynamic range and capture all the details.

ISO Setting: Tips for Different Situations

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

• Bright Daylight: In well-lit conditions like sunny days, I use low ISO settings like ISO 100 or 200 to get the best image quality. This will minimize noise and make your images sharp and detailed.
• 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 and how much noise you can tolerate. In the early days, I could keep raising the ISO and 'get the shot' - I felt freedom - it was great. But I would get home and discover that the images were too noisy to be usable; I look great shots. So 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 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 higher ISO, especially in not-so-good lighting conditions. Balancing ISO with shutter speed and aperture is critical to getting 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 in controlled lighting conditions, like when I shoot in the studio, I always aim for low ISO to get smooth skin tones and no 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 my street portraits, I could quite often shoot at 800 or 1200 ISO.
• Landscape: Landscapes are often shot with low ISO to get detail across the whole image, especially when using a narrow aperture for deep depth of field. However, you should ease the ISO in low light conditions to avoid camera shaking during more prolonged exposure. Here, the tradeoff is shutter speed. Using a sturdy tripod, I could increase my exposure time to 30 seconds or even a few minutes to keep my ISO at the optimum 100 ISO.

Conclusion

Mastering ISO in photography is an essential skill that can significantly improve your ability to capture fantastic 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 and try different ISOs in different conditions to see how they affect your images. The more you understand how ISO works with other camera settings, the better you'll get the shot, no matter 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. Happy shooting!