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What is ISO: An In-Depth Explanation
by Keenan Hursh
In today’s article, we’re diving into the third and final pillar of the exposure triangle: ISO. In my two previous articles, we discussed Shutter Speed and Aperture, taking a deep dive into both of these concepts and exploring exactly what they are and how they affect the way light enters your camera to form an image. Today, we’re wrapping up the story with a thorough examination of ISO.
As I’m sure you’ve heard, having a solid understanding of the exposure triangle and the fundamentals of exposure, in general, is absolutely essential no matter where you are in your photography journey. If you’re just getting started or want a refresher on these fundamentals, then this article is for you. I’d also recommend reading my previous articles on Shutter Speed and Aperture if you haven’t already.
So, let’s get into it. Let’s take a deep dive into ISO and cover all the basics including what exactly it is, how it works, and how it will alter the look and feel of your images.
As I’m sure you’ve heard, having a solid understanding of the exposure triangle and the fundamentals of exposure, in general, is absolutely essential no matter where you are in your photography journey. If you’re just getting started or want a refresher on these fundamentals, then this article is for you. I’d also recommend reading my previous articles on Shutter Speed and Aperture if you haven’t already.
So, let’s get into it. Let’s take a deep dive into ISO and cover all the basics including what exactly it is, how it works, and how it will alter the look and feel of your images.
What Is ISO?
ISO, which stands for the International Organization for Standardization, is a standardized scale used to measure the sensitivity of a camera's digital image sensor to light. The ISO scale typically starts at around 100 and can go as high as 51200, or even higher in advanced mirrorless cameras.
Before digital cameras came around, in the world of film or analog photography, you had to choose between a wide range of films with different film speeds. The film speed was the exact same thing as ISO and was a standard measurement of a film’s sensitivity to light. Of course, it was nice to be able to choose from a wide variety of options but once you put a roll in your camera you were relatively limited in the ideal lighting conditions for your given film speed. With modern digital cameras, we now have much more freedom and can easily change our ISO with the turn of a dial. But how does the image sensor actually change its sensitivity to light?
Inside your camera's image sensor, there are millions of tiny light-sensitive photosites, also known as pixels. Each photosite is responsible for capturing and converting light into an electrical signal, which ultimately forms the digital image. The sensitivity of these photosites to light is controlled by adjusting the ISO setting. If you increase your ISO, each site becomes more sensitive to light and vice versa.
When you set a higher ISO value, the camera increases the amplification of the electrical signal produced by each photosite. This amplification effectively boosts the sensor's sensitivity to light, allowing it to capture more light in low-light conditions. On the other hand, setting a lower ISO value reduces the amplification, resulting in reduced sensitivity to light and better performance in well-lit situations.
By adjusting the ISO setting, you can tailor the camera's sensitivity to light according to the specific lighting conditions you encounter. This flexibility empowers you to capture properly exposed images even in challenging lighting situations.
ISO, which stands for the International Organization for Standardization, is a standardized scale used to measure the sensitivity of a camera's digital image sensor to light. The ISO scale typically starts at around 100 and can go as high as 51200, or even higher in advanced mirrorless cameras.
Before digital cameras came around, in the world of film or analog photography, you had to choose between a wide range of films with different film speeds. The film speed was the exact same thing as ISO and was a standard measurement of a film’s sensitivity to light. Of course, it was nice to be able to choose from a wide variety of options but once you put a roll in your camera you were relatively limited in the ideal lighting conditions for your given film speed. With modern digital cameras, we now have much more freedom and can easily change our ISO with the turn of a dial. But how does the image sensor actually change its sensitivity to light?
Inside your camera's image sensor, there are millions of tiny light-sensitive photosites, also known as pixels. Each photosite is responsible for capturing and converting light into an electrical signal, which ultimately forms the digital image. The sensitivity of these photosites to light is controlled by adjusting the ISO setting. If you increase your ISO, each site becomes more sensitive to light and vice versa.
When you set a higher ISO value, the camera increases the amplification of the electrical signal produced by each photosite. This amplification effectively boosts the sensor's sensitivity to light, allowing it to capture more light in low-light conditions. On the other hand, setting a lower ISO value reduces the amplification, resulting in reduced sensitivity to light and better performance in well-lit situations.
By adjusting the ISO setting, you can tailor the camera's sensitivity to light according to the specific lighting conditions you encounter. This flexibility empowers you to capture properly exposed images even in challenging lighting situations.
How Does ISO Affect an Image?
Understanding how ISO affects the appearance of your images is crucial for controlling the final result. As previously explained, a higher ISO will increase your sensor’s sensitivity to light which is great for shooting in low-light conditions. But this increased sensitivity comes at a cost.
It's important to note that while higher ISO settings provide increased sensitivity, they also introduce more electronic noise. Electronic noise appears as grain or speckles in your images and can affect overall image quality. It’s very important to take this into account when shooting in low light situations and make sure you don’t set your ISO too high. Advanced camera models often employ noise reduction algorithms to mitigate this noise to some extent, but the trade-off between noise and increased sensitivity remains.
When shooting at a lower ISO, such as ISO 100 or 200, the camera's sensor is less sensitive to light, resulting in a lower level of image noise or grain. This is ideal for capturing images in well-lit environments or when you want to achieve a crisp and clean look. You can also shoot at lower ISOs even when there’s a lack of environmental light by using a tripod and longer shutter speeds.
On the other hand, using a higher ISO, such as ISO 800 or above, increases the sensor's sensitivity to light, making it more capable of capturing images in darker conditions. However, the trade-off is that higher ISO settings tend to introduce more image noise or grain, which can result in a loss of detail and decreased overall image quality. It's important to strike a balance between the desired exposure and acceptable image noise levels when selecting the appropriate ISO setting.
It's also worth noting that there are many great photo editing software tools currently available that can reduce or eliminate noise from an image. Adobe Illustrator recently announced their own noise-reduction tool, and it works great!
Understanding how ISO affects the appearance of your images is crucial for controlling the final result. As previously explained, a higher ISO will increase your sensor’s sensitivity to light which is great for shooting in low-light conditions. But this increased sensitivity comes at a cost.
It's important to note that while higher ISO settings provide increased sensitivity, they also introduce more electronic noise. Electronic noise appears as grain or speckles in your images and can affect overall image quality. It’s very important to take this into account when shooting in low light situations and make sure you don’t set your ISO too high. Advanced camera models often employ noise reduction algorithms to mitigate this noise to some extent, but the trade-off between noise and increased sensitivity remains.
When shooting at a lower ISO, such as ISO 100 or 200, the camera's sensor is less sensitive to light, resulting in a lower level of image noise or grain. This is ideal for capturing images in well-lit environments or when you want to achieve a crisp and clean look. You can also shoot at lower ISOs even when there’s a lack of environmental light by using a tripod and longer shutter speeds.
On the other hand, using a higher ISO, such as ISO 800 or above, increases the sensor's sensitivity to light, making it more capable of capturing images in darker conditions. However, the trade-off is that higher ISO settings tend to introduce more image noise or grain, which can result in a loss of detail and decreased overall image quality. It's important to strike a balance between the desired exposure and acceptable image noise levels when selecting the appropriate ISO setting.
It's also worth noting that there are many great photo editing software tools currently available that can reduce or eliminate noise from an image. Adobe Illustrator recently announced their own noise-reduction tool, and it works great!
What ISO Should I Use for a Specific Style of Photography?
Now that we’ve looked at how ISO can greatly affect the appearance of a photograph let’s take it one step further and discuss what ISO settings are common in different styles of photography. Of course, these are just general guidelines, and the ideal ISO level will change depending on conditions and personal preference.
Landscape Photography:
Landscape photographers often strive to capture images with maximum sharpness and detail. In well-lit landscapes, lower ISO settings such as ISO 100 or 200 are commonly used. By keeping the ISO low, photographers can achieve optimal image quality and ensure crisp details throughout the scene without any unwanted noise. Tripods are also frequently employed to stabilize the camera, allowing for longer exposure times without the need for high ISO settings.
Wildlife Photography:
Photographing wildlife often requires a flexible approach to ISO settings due to changing lighting conditions and the need to freeze motion. In well-lit situations, lower ISO values can be used to capture sharp and noise-free images. However, in low-light scenarios or when photographing fast-moving subjects, higher ISO values, typically ranging from 400 to 1600 or higher, may be necessary to maintain a fast shutter speed and freeze the action.
Long-Exposure Photography:
Long-exposure photography involves using extended exposure times to capture creative effects such as light trails, smooth water, or starry skies. When shooting long exposures with ample light, it's common to use the lowest native ISO of your camera, typically ISO 100 or 200, to maintain maximum image quality. By utilizing a tripod and longer exposure times, photographers can compensate for the low ISO setting while capturing stunning long-exposure images.
Night Sky Photography:
Photographing the night sky, including stars, the Milky Way, and astrophotography, presents unique challenges. This is a form of long-exposure photography but the key difference is that there is often very little ambient light to work with. To capture the faint light of the night sky, higher ISO settings ranging from 1600 to 6400 or even higher are often employed. Higher ISO values allow the camera's sensor to gather more light and reveal the intricate details of the night sky.
However, it's important to carefully manage noise levels at high ISO settings. Advanced cameras with better noise performance can help minimize the impact of noise on image quality. Additionally, post-processing techniques such as noise reduction can be applied to reduce noise without sacrificing critical details.
Portrait Photography:
When it comes to portrait photography, the choice of ISO setting depends on the available light and the desired mood. In well-lit studio environments or outdoor settings with ample natural light, lower ISO values such as ISO 100 or 200 are commonly used. These lower ISO settings help maintain image sharpness and minimize noise, resulting in clean and detailed portraits.
However, in low-light situations or when shooting indoors with limited lighting, higher ISO values may be necessary to ensure proper exposure without sacrificing shutter speed. It’s also quite common to use a wide-open aperture in portrait photography allowing you to use lower ISO values.
Now that we’ve looked at how ISO can greatly affect the appearance of a photograph let’s take it one step further and discuss what ISO settings are common in different styles of photography. Of course, these are just general guidelines, and the ideal ISO level will change depending on conditions and personal preference.
Landscape Photography:
Landscape photographers often strive to capture images with maximum sharpness and detail. In well-lit landscapes, lower ISO settings such as ISO 100 or 200 are commonly used. By keeping the ISO low, photographers can achieve optimal image quality and ensure crisp details throughout the scene without any unwanted noise. Tripods are also frequently employed to stabilize the camera, allowing for longer exposure times without the need for high ISO settings.
Wildlife Photography:
Photographing wildlife often requires a flexible approach to ISO settings due to changing lighting conditions and the need to freeze motion. In well-lit situations, lower ISO values can be used to capture sharp and noise-free images. However, in low-light scenarios or when photographing fast-moving subjects, higher ISO values, typically ranging from 400 to 1600 or higher, may be necessary to maintain a fast shutter speed and freeze the action.
Long-Exposure Photography:
Long-exposure photography involves using extended exposure times to capture creative effects such as light trails, smooth water, or starry skies. When shooting long exposures with ample light, it's common to use the lowest native ISO of your camera, typically ISO 100 or 200, to maintain maximum image quality. By utilizing a tripod and longer exposure times, photographers can compensate for the low ISO setting while capturing stunning long-exposure images.
Night Sky Photography:
Photographing the night sky, including stars, the Milky Way, and astrophotography, presents unique challenges. This is a form of long-exposure photography but the key difference is that there is often very little ambient light to work with. To capture the faint light of the night sky, higher ISO settings ranging from 1600 to 6400 or even higher are often employed. Higher ISO values allow the camera's sensor to gather more light and reveal the intricate details of the night sky.
However, it's important to carefully manage noise levels at high ISO settings. Advanced cameras with better noise performance can help minimize the impact of noise on image quality. Additionally, post-processing techniques such as noise reduction can be applied to reduce noise without sacrificing critical details.
Portrait Photography:
When it comes to portrait photography, the choice of ISO setting depends on the available light and the desired mood. In well-lit studio environments or outdoor settings with ample natural light, lower ISO values such as ISO 100 or 200 are commonly used. These lower ISO settings help maintain image sharpness and minimize noise, resulting in clean and detailed portraits.
However, in low-light situations or when shooting indoors with limited lighting, higher ISO values may be necessary to ensure proper exposure without sacrificing shutter speed. It’s also quite common to use a wide-open aperture in portrait photography allowing you to use lower ISO values.
Conclusion
To wrap things up, ISO is a fundamental aspect of photography that directly impacts the exposure and appearance of your images. Along with shutter speed and aperture, ISO forms one corner of the exposure triangle, and understanding how these elements all work together is strongly recommended. By understanding how ISO works and its effects on your photos, you can confidently choose the appropriate ISO setting for any given situation. Lower ISO values yield cleaner images with less noise, while higher ISO values enhance your camera's ability to capture images in low-light conditions.
It's important to strike a balance between the desired exposure, noise levels, and image quality when selecting the ISO setting. Different styles of photography require specific approaches to ISO settings, taking into consideration the available light, desired sharpness, and creative vision.
By experimenting with different ISO settings and understanding their effects, you can enhance your photography skills and capture stunning images in various lighting conditions. So, embrace the power of ISO and let it be your ally in creating visually captivating photographs.
As always, I hope this article has been informative and helpful. Get out there and experiment with ISO in your own backyard and I wish you all the best of luck on your next photography adventure. Until next time!
To wrap things up, ISO is a fundamental aspect of photography that directly impacts the exposure and appearance of your images. Along with shutter speed and aperture, ISO forms one corner of the exposure triangle, and understanding how these elements all work together is strongly recommended. By understanding how ISO works and its effects on your photos, you can confidently choose the appropriate ISO setting for any given situation. Lower ISO values yield cleaner images with less noise, while higher ISO values enhance your camera's ability to capture images in low-light conditions.
It's important to strike a balance between the desired exposure, noise levels, and image quality when selecting the ISO setting. Different styles of photography require specific approaches to ISO settings, taking into consideration the available light, desired sharpness, and creative vision.
By experimenting with different ISO settings and understanding their effects, you can enhance your photography skills and capture stunning images in various lighting conditions. So, embrace the power of ISO and let it be your ally in creating visually captivating photographs.
As always, I hope this article has been informative and helpful. Get out there and experiment with ISO in your own backyard and I wish you all the best of luck on your next photography adventure. Until next time!
To learn more about the exposure triangle and ISO, be sure to check out these additional articles:
What is Shutter Speed: An In-Depth Explanation - Keenan Hursh
What is Aperture: An In-Depth Explanation - Keenan Hursh
Understanding the Exposure Triangle - Kenton Krueger
Understanding ISO - Chris Gheen
What is Shutter Speed: An In-Depth Explanation - Keenan Hursh
What is Aperture: An In-Depth Explanation - Keenan Hursh
Understanding the Exposure Triangle - Kenton Krueger
Understanding ISO - Chris Gheen
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AUTHOR
Keenan is an avid photographer, digital creator, and lover of the outdoors currently based out of Bozeman, Montana. He is originally from Boulder, Colorado where he developed a deep passion for getting outside and pursuing outdoor activities including skiing, cycling, hiking, rafting, backpacking and more. Recently he has developed new passions for paragliding as well as designing and sewing outdoor adventure gear for cyclists and hikers.
At a very young age, Keenan started bringing a camera along on his excursions and immediately fell in love with the art of photography. He started out with his parent’s cheap point and shoot and has continuously improved his craft and gear refining his shooting style and producing more compelling and intriguing images. He pursues a wide range of photography styles primarily shooting landscapes, wildlife, adventure photography, and enjoys shooting analog on 35mm film every now and then.
Since graduating from the University of Denver with a degree in Emergent Digital Practices, Keenan has pursued a professional career in digital marketing, graphic design, and content creation. He has benefitted a wide range of companies and organizations from small start-ups to well known agencies and brands.
You can view Keenan’s photography and graphic design work on his website at www.keenanhurshmedia.com
At a very young age, Keenan started bringing a camera along on his excursions and immediately fell in love with the art of photography. He started out with his parent’s cheap point and shoot and has continuously improved his craft and gear refining his shooting style and producing more compelling and intriguing images. He pursues a wide range of photography styles primarily shooting landscapes, wildlife, adventure photography, and enjoys shooting analog on 35mm film every now and then.
Since graduating from the University of Denver with a degree in Emergent Digital Practices, Keenan has pursued a professional career in digital marketing, graphic design, and content creation. He has benefitted a wide range of companies and organizations from small start-ups to well known agencies and brands.
You can view Keenan’s photography and graphic design work on his website at www.keenanhurshmedia.com
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All Images & Content are property of Backcountry Journeys Photography Tours, Workshops & Safaris LLC - Copyright 2024
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