What is ISO in Photography? Complete Guide for Beginners

As a portrait photographer, I vividly remember the moment when I first encountered the term “ISO” in my photography journey. I was a beginner, eager to capture stunning portraits, but I found myself puzzled by this seemingly cryptic acronym.

Was it some complex technical jargon or a secret code that only professional photographers understood? Little did I know that ISO was a fundamental concept that would significantly impact my photography.

Let me take you on a journey to demystify ISO and its significance in photography. Like many beginner photographers, I was once puzzled by this mysterious setting on my camera. I remember the frustration of grainy photos and missed opportunities due to improper ISO settings. But with time and practice, I unlocked the true potential of ISO, and it transformed my photography.

If you’re a beginner looking to level up your photography skills, understanding ISO is essential. It’s the key to unlocking creative control, mastering low-light situations, and achieving the desired image quality in your photos. With the right knowledge and techniques, you can confidently navigate ISO settings and create stunning images in any lighting conditions.

In this beginner’s guide to ISO in photography, I’ll share my insights and practical tips to help you harness the power of ISO. So, grab your camera, let’s dive into the world of ISO, and elevate your photography to new heights!

What is ISO in Photography?

ISO in photography determines how much light your camera’s sensor needs to capture a well-exposed image.

Watch the video covering this section of the guide:

What is ISO in Photography? EXPLAINED in 5 MINUTES

ISO, which stands for International Organization for Standardization, is a measure of the sensitivity of your camera’s image sensor to light. It originated from the film photography days when films with different sensitivities to light were labeled with ISO ratings.

Before we dive into how ISO affects your images, it’s first important to understand the role ISO plays in the “exposure triangle.”

Also, it’s important to note that in this guide, everything I’m referring to is only when you put your camera in manual shooting mode.

ISO and the Exposure Triangle

Understanding ISO is crucial because it’s closely tied to two other key elements in photography: aperture and shutter speed. The trio of ISO, aperture, and shutter speed forms the exposure triangle, which determines the brightness, sharpness, and overall quality of your photos.

iso and the exposure triangle
ISO in the exposure triangle

We’ve covered what ISO is which determines the sensitivity of the sensor to light — so what are aperture and shutter speed?

Aperture refers to the size of the camera’s aperture opening, which controls the amount of light that enters the camera. Shutter speed, on the other hand, determines the length of time that the camera’s sensor is exposed to light.

All three components work together to affect the exposure of an image. They are all used to balance the exposure out. So in the case of ISO, it will act as a tool to balance the exposure in shooting situations where aperture and shutter speed alone may not provide the desired exposure results.

For example, in a low-light situation where using a wider aperture such as f/1.8 or f/2.4 or a longer shutter speed such as under 1/100 would result in a blurred image, increasing the ISO could help achieve a properly exposed photo without sacrificing image quality.

Conversely, in a bright outdoor situation where you may need to use a narrow aperture (higher f-stop number) or faster shutter speed to control the amount of light entering the camera, then lowering the ISO could help prevent overexposure and maintain image quality.

It’s important to understand that changing the ISO can affect the exposure of the image, but can also impact the image quality and noise levels as well which I’ll touch on later. Therefore, finding the right balance between ISO, aperture, and shutter speed is crucial in achieving your desired exposure while also maintaining good image quality.

As a photographer, experimenting with different combinations of ISO, aperture, and shutter speed in different shooting conditions can help you understand how they work together and how to use them effectively to achieve the desired exposure and image quality for your photos.

Let’s take a look at some more scenarios in order to get a better understanding of how ISO works alongside aperture and shutter speed within the exposure triangle:

Low-Light Indoor Portraits:

If photographing a low-light indoor portrait, here is what your ISO, aperture, and shutter speed could look like:

  • Higher ISO: If you’re shooting indoors with limited available light, you may need to increase your ISO to a higher value (e.g., ISO 1600 or higher) to make the image brighter and capture enough light for a properly exposed portrait. However, keep in mind that higher ISO values can introduce more noise or grain in the image.
  • Wider aperture: A wider aperture (e.g., f/1.8 or wider) can help you capture more light and achieve a shallow depth of field, which can create a nice bokeh effect and isolate your subject from the background.
  • Slower shutter speed: To compensate for the low light, you may need to use a slower shutter speed (e.g., 1/60s or slower) to allow more light to reach the camera sensor. However, you’ll need to use a tripod or stabilize your camera to avoid camera shake.

Bright Outdoor Landscapes

If photographing a bright outdoor landscape, here is what your ISO, aperture, and shutter speed could look like:

  • Lower ISO: In a bright outdoor setting, you may need to lower your ISO to a lower value (e.g., ISO 100 or lower) to avoid overexposure and maintain good image quality.
  • Narrower aperture: A narrower aperture (e.g., f/11 or smaller) can help you control the amount of light entering the camera and achieve a larger depth of field, which is often desired in landscape photography to keep the entire scene in focus.
  • Faster shutter speed: To prevent overexposure and maintain proper exposure, you may need to use a faster shutter speed (e.g., 1/250s or faster) to limit the amount of light reaching the camera sensor.

Action Sports Photographs

  • Higher ISO: When capturing fast-moving subjects in action sports, you may need to increase your ISO to a higher value (e.g., ISO 800 or higher) to use a faster shutter speed and freeze the motion.
  • Wide aperture: A wide aperture (e.g., f/2.8 or wider) can help you achieve a faster shutter speed and freeze the action by allowing more light to enter the camera and reach the sensor.
  • Fast shutter speed: To capture fast action without motion blur, you’ll need to use a fast shutter speed (e.g., 1/1000s or faster) to freeze the motion and get sharp images.

Now that we’ve covered how ISO plays its part in the exposure triangle, let’s take a look at all the ways ISO affects a photo.

How Does ISO Affect a Photo?

ISO affects your photo in three main ways. Let’s take a look at how ISO affects your photos:

1. Exposure

The first way ISO affects your photos is through the overall exposure of your image. As we’ve touched on in the previous section, ISO is one of the three components in the exposure triangle.

When you increase the ISO, you are essentially making your camera’s sensor more sensitive to light, allowing your camera to capture more light and produce a brighter image. Conversely, lowering the ISO number makes the camera sensor less sensitive to light, resulting in a darker image.

This means that if you are photographing in a situation where there is not much light such as at night or in an indoor situation, then increasing the ISO can be beneficial as it will allow you to capture a properly exposed image without having to rely on a longer shutter speed or wider aperture.

On the other hand, if you’re photographing a bright outdoor situation, you may want to use a lower ISO setting so you don’t have a blown-out, overexposed image.

high iso means more sensitive to light
less ISO means less sensitive to light
quick way to remember ISO

2. Image Quality

The second way ISO affects your photos is through image quality.

When I first started using ISO, I made the mistake of cranking it up to the highest value, thinking it would make my photos brighter. But I soon realized that higher ISO settings can introduce unwanted noise or grain in photos, resulting in decreased image quality.

On the other hand, using a lower ISO setting in low-light situations can result in underexposed images. It was clear that I needed to strike the right balance with ISO to achieve the best results.

As a photographer, it’s important to be mindful of the trade-off between higher ISO settings for brighter exposures and potential noise in your images.

I recommend practicing and familiarizing yourself with your camera’s ISO performance to understand its limitations so that when you’re out on a photo shoot, you have a general idea of what ISO to use without getting grain or noise.

And one thing I had to come to grips with as a photographer is that if your camera can’t handle high ISO well and you like to shoot in dark or low-light situations such as nightclubs or concert venues, then you either need to get a better camera that handles higher ISOs better without producing noise or find a light source in your current low-light setting.

3. Noise or Grain

The third way ISO affects your photos is through the addition of noise or grain.

We’ve already been discussing noise or grain which is a byproduct of taking an image with very high ISO, but I wanted to dive into it a bit more so you understand.

The presence of noise or grain in an image can be a creative choice or a distraction, depending on the type of photography you’re doing and the desired aesthetic.

Some photographers like to take a perfectly sharp image and then add artificial grain in post-production to give it that film/vintage look.

Some photographers also intentionally use a higher ISO setting to achieve a grainy or gritty look in their photos to add some moodiness or nostalgia to the image.

This is perfectly fine when you’re taking a photo for your own pleasure whether it’s a street photograph, portrait, landscape, etc. In fact, I’d recommend trying this out just so you can further explore your own camera’s ISO limitations and what the noise/grain will look like at different ISO values.

On the other hand, if you’re taking a portrait or wedding photo for a client, then you will want to capture a more professional, fine-detail, smooth-tone image. In this case, a higher ISO setting for creative effects may not be desirable as it can affect the overall image quality.

high ISO causing grain in image
noise in the image due to high ISO

Common ISO Values

Before diving into knowing what ISO to use, let’s cover some common ISO values you should know in order to understand the ISO ranges:

Watch the video covering this section of the guide:

Stop Guessing – Common ISO Values You NEED to Know


Low ISO values typically range from ISO 100-200.

You will usually use low ISO values when you are in a well-lit situation such as outdoors during the day time or in an indoor or studio setting where there is ample lighting.

Low ISO values will produce very minimal to essentially no noise or grain in the image creating a high image quality with sharp details.

Moderate ISO

Moderate ISO values typically range from ISO 400-800.

You will usually use moderate ISO values when you are in a situation where the lighting is less ideal such as when you are indoors or in a studio with moderate to low lighting. If you are outside, then times during dusk or dawn are when you will most likely need to use moderate ISO values.

Moderate ISO values provide a good balance between image quality and sensitivity to light allowing for good image quality while still managing noise or grain levels.

High ISO

High ISO values typically range from ISO 1600-3200.

You will usually use high ISO values when in a low-light situation or when photographing a fast-moving subject such as someone sprinting, a car, or an animal — where a higher sensitivity to light is needed.

High ISO values introduce more noise or grain into the image but the amount depends on the type of camera you have and how it handles high ISO values.

Depending on your camera’s ability to handle high ISO values, you may see a degradation in image quality, reduced sharpness, or an impact on overall color accuracy.

How to Know What ISO to Use?

Now that we know the fundamentals of ISO, let’s take a closer look at how to know what ISO to use based on your current shooting situation.

Watch the video covering this section of the guide:

How to Choose The Correct ISO Setting – 5 EASY Tips

1. Assess the Available Lighting

The first step in order to figure out what ISO to use is to assess the available lighting in your current environment.

If you are in a bright or well-lit environment such as a studio setting with lots of light or outdoors on a sunny day, then you’ll want to use a lower ISO value to achieve optimal image quality.

Conversely, if you are in a dark environment such as photographing in a nightclub, concert, or dimly lit venue, then you may want to use a higher ISO value.

2. Consider the Desired Image Quality

The second step in order to figure out what ISO to use is to consider the desired image quality you want to achieve.

As mentioned, lower ISO values will produce images with less noise or grain and vice versa when using higher ISO values.

You will need to consider the trade-off between the need for more light sensitivity and the desired image quality for your specific photograph.

If you are photographing for client work, then you may not want to take that higher ISO shot with lots of grain as the client may be upset with the image quality. If you are photographing to just experiment and practice, then go for it, and in fact, I recommend it so you can see how your camera handles it.

3. Consider Your Subject and Creative Intent

The third step in order to figure out what ISO to use is to consider your subject and the creative intent you want with your image as this will influence which ISO setting you will use.

For example, if you’re photographing a fast-moving subject and need to “freeze the action,” you will need to use a very fast shutter speed which will call for a higher ISO value.

On the other hand, if you are photographing a subject that is not moving such as with landscapes, portraits, products, or headshots, you will have more flexibility to use a lower ISO value.

4. Test and Experiment With Your Camera

The fourth step in order to figure out what ISO you should use is to test and experiment with your camera.

As mentioned earlier, every camera performs differently at different ISO values so it’s crucial that you test and experiment with your camera to understand its ISO performance in terms of boundaries.

Take sample shots at different ISO settings so you can review the results and see how the noise or grain levels vary and how they impact image quality.

This will help you become familiar with your camera’s ISO capabilities and allow you to make quicker, more informed decisions on what ISO to use in different photography scenarios.

5. Practice and Experience

The fifth and final step in order to know what ISO to use is to practice, practice, practice.

The more you photograph in different lighting conditions and experiment with different ISO settings, then the better you will become at intuitively knowing what ISO to use for any given situation.

With more and more experience, you will develop a better understanding of your camera’s ISO performance and what ISO values you can push it to.

You’ll also be able to assess a setting quicker in terms of knowing what ISO to use.

All-in-all, you can think of these five steps as a loop where you consider the current lighting situation, desired image quality, and subject, and then you pick an ISO number, see how it looks, and then try another number until you are happy with the results and you keep practicing this.

Over time, your photographic eye and knowledge of your camera’s ISO values will allow you to walk into a scene and be able to know (if not be very close) to knowing what ISO value is needed without needing to test it.

Now that we’ve covered the steps, let’s dive into additional tips you should know when using ISO in photography.

Tips for Using ISO in Photography

Here are some practical tips I use that you should start using when it comes to ISO in photography:

Watch the video covering this section of this guide:

Struggling With ISO? – Try These 5 EASY Tips

1. Use the Lowest ISO Possible

The first tip is to use the lowest ISO possible as this will allow you to achieve the desired exposure.

Lower ISO values generally produce images with less noise or grain and higher image quality. With that being said, I recommend starting with the lowest ISO setting and only increasing it when necessary.

2. Balance ISO With Other Exposure Settings

The second tip is to balance your ISO with other exposure settings.

As we’ve touched on at the beginning of this guide, ISO is a part of the exposure triangle along with shutter speed and aperture.

With that being said, when adjusting ISO, consider how it will interact with your shutter speed and aperture based on your desired image results.

For example, if you increase the ISO to capture more light, you may need to adjust your shutter speed or aperture to maintain proper exposure — but it may throw off another creative choice you had in mind such as a blurred background with a wider aperture. So overall, it’s important to balance all three of these elements of the exposure triangle.

3. Leverage Your Camera’s Light Meter

The third tip is to leverage your camera’s light meter which is built into most cameras.

Your camera’s light meter measures the amount of light in the scene and provides feedback on the exposure settings.

With that being said, when using ISO, it’s important to check and use your camera’s light meter to ensure proper exposure and adjust the different elements in the exposure triangle to ensure your indicator on the light meter still shows that your image is well-exposed.

4. Consider a Tripod or Image Stabilization

The fourth tip when using ISO is to consider a tripod or propping your camera on something to stabilize it in situations where you need to use a higher ISO to capture enough light but want to minimize noise.

Doing this can help reduce camera shake which can contribute to increased noise in images and will allow you to lower the shutter speed in case you have a high ISO but still need more exposure.

5. Post-Process for Noise Reduction

The fifth tip is to post-process for noise reduction.

If you do end up with noise or grain in your images, consider using noise reduction techniques in post-production to help minimize the noise and improve your overall image quality.

There are various post-processing software and tools for you to use. For example, Adobe Photoshop and Lightroom have built-in tools to reduce the noise in the image, which I’ll be touching on a bit more later.

Now that we’ve touched on some of the tips you should use, let’s touch on the difference between using ISO in digital and film photography so you know the difference.

ISO in Digital Photography

ISO in digital photography is what most of this guide was covering.

To recap, ISO in digital photography refers to the sensitivity of the camera’s image sensor to light and is an important setting that allows you to adapt to different lighting conditions.

Understanding how ISO works in digital photography and how it can impact image quality can help you effectively use ISO to achieve desired exposure and produce high-quality images in various shooting situations.

ISO in Film Photography

ISO in film photography is different than digital photography.

When you use a film camera, you need to purchase film and there are many different types of film each with its own ISO rating.

Unlike digital photography where ISO can be adjusted on the camera, in film photography, the ISO is determined in the film itself.

Once a roll of film is loaded into the camera, the ISO of the film cannot be changed until the roll is finished and a new roll is loaded.

Film comes in various ISO ratings, such as ISO 100, ISO 200, ISO 400, ISO 800, and so on. These ISO ratings are similar to the ISO values we touched on based on the different shooting scenarios.

Lower ISO films, such as ISO 100 or ISO 200, are typically used for bright, well-lit situations, while higher ISO films, such as ISO 400 or above, are used for low-light or dimly-lit environments where more sensitivity to light is needed.

When it comes to the grain and noise levels, it will be apparent in higher ISO levels — which we’ve already covered.

Since using film cameras these days is mostly to achieve that vintage vibe and aesthetic look, some photographers intentionally use high ISO films to create a specific look or mood in their photos while other prefer the lower ISO films for the fine grain and sharpness. It’s up to you at the end of the day.

Creative Use of ISO in Photography

As I gained experience, I learned how to leverage ISO creatively. I experimented with different ISO settings to capture unique effects, such as using a higher ISO for a gritty, film-like look or a lower ISO for a long exposure to create a dreamy motion blur. ISO became my ally in capturing stunning portraits in various lighting conditions, from bright sunny days to dimly lit indoor settings.

With time and practice, I realized that ISO was not just a technical setting but a powerful tool that allowed me to achieve my creative vision. It gave me the flexibility to adapt to different lighting conditions, control image quality, and create unique visual effects in my portraits.

We’ve already touched on some of these, but let’s take a look at the way you can use ISO creatively in your photography:

1. High ISO for Intentional Grain

As mentioned, higher ISO values will introduce noise and grain into the image, which can either be a nuisance or be used to creatively add a vintage or gritty look to your images.

This can be particularly desired in street photography, urban landscapes, or moody portraits where you are going for a grainy aesthetic.

surfer on the beach
intentionally adding grain to this image

2. High ISO and Fast Shutter Speed

If you are photographing moving at a really fast speed and want to capture that “freeze frame” look, then you will have to use a fast shutter speed.

If you want to use a really fast shutter speed, you will need more light so you will have to use a higher ISO (depending on the lighting situation of course).

freeze frame on car driving
capturing that “freeze frame” look

3. Low ISO and Slow Shutter Speed

If you are photographing something moving and want to capture that motion blur effect such as a waterfall or light trail, then you will have to use a slow shutter speed.

If you want to use a slow shutter speed, then this means lots of light will enter the camera sensor which will require you to use a lower ISO number.

In summary, there are many unique and artistic choices that you can implement with ISO and the rest of the exposure triangle, but these are my favorite.

I recommend playing around with the different combinations to find what interests you creatively.

capturing blurry water look
capturing blurry water look

Fixing ISO in Post-Production

In some cases, you may find that your photos have noise or grain in them due to a higher ISO setting used.

Fortunately, there are ways you can help recover some if not most of the image quality in post-production:

1. Noise Reduction Tool

Many popular post-production tools such as from the Adobe Suite of products like Adobe Photoshop or Lightroom have built-in noise reduction sliders.

Simply slide the slider to the left to reduce the amount of noise in your images.

The only downside with this is that it tends to “smooth out” the image making it less sharp. So if you have large amounts of noise in the image you’re trying to get rid of, then you may end up with a smooth image.

2. Selective Sharpening

Selective sharpening is another approach to fixing ISO noise in post-production and can be a useful technique after the previous one described.

As mentioned, using noise reduction tools in the software can often smoothen out the image.

With that being said, you can apply selective sharpening with the Sharpening Tools to the areas that need it to help restore some detail and clarity back.

3. Localized Adjustment Tools

Many photo editing softwares have localized adjustment tools in the form of brushes or masks.

Instead of taking a blanket approach to the noise reduction tool and using it on the whole image, you can selectively apply adjustments to the specific areas of the image and then reduce the noise on those specific parts.

For example, if you have a person in the photograph, you can apply a mask on them and only reduce the noise on them.

Overall, it’s important to strike a balance between noise reduction and retaining image details.

Final Thoughts

Overall, I hope you took away something valuable from the guide on ISO in photography.

The best way to learn ISO is to just go out and start paying attention to ISO and how the other components of the exposure triangle affect the exposure during different lighting situations.

After some practice, you’ll be able to approach a scene and know which ISO you should use automatically based on your previous experiences. So go out there, use that ISO, and happy photographing!

Frequently Asked Questions

What is the difference between ISO 400 and 800?

ISO 400 and ISO 800 are both higher ISO settings compared to lower ISO values, such as ISO 100 or 200. The main difference between ISO 400 and ISO 800 is that ISO 800 is one stop higher than ISO 400, meaning it is twice as sensitive to light, allowing for faster shutter speeds or smaller apertures in low light conditions. However, higher ISO settings like ISO 800 may also introduce more noise or grain in the image compared to ISO 400, so it’s important to balance the need for increased sensitivity with the potential for decreased image quality.

What is the best ISO for sports photography?

The best ISO for sports photography depends on various factors, such as the lighting conditions, the speed of the action, and the capabilities of your camera. In general, using a higher ISO, such as ISO 800 or above, can help you achieve faster shutter speeds to freeze fast-moving subjects and capture action shots with minimal motion blur, but it may also introduce more noise in the image. It’s recommended to test different ISO settings in the specific sports photography conditions you’re shooting in to find the optimal balance between sensitivity and image quality for your specific camera and situation.

What is ISO sensitivity in photography?

ISO sensitivity in photography refers to the camera’s ability to capture and process light in different lighting conditions. It determines the camera’s sensitivity to light, with higher ISO values making the camera more sensitive to light and lower ISO values making it less sensitive. ISO sensitivity is an important setting that allows photographers to adjust the exposure and image quality based on the available light in a scene, and it plays a crucial role in achieving properly exposed and noise-free images.

What is the best ISO for outdoor photography?

The best ISO for outdoor photography depends on various factors, including the lighting conditions, the desired image quality, and the capabilities of your camera. In general, using the lowest native ISO of your camera, such as ISO 100 or 200, is recommended for outdoor photography in bright, well-lit conditions to achieve the best image quality with minimal noise. However, you may need to increase the ISO in low-light situations to maintain proper exposure, and finding the optimal ISO setting for your specific camera and shooting conditions may require some experimentation and testing.

What is the best ISO for night photography?

The best ISO for night photography depends on various factors, including the amount of available light, the desired level of noise in the image, and the capabilities of your camera. In general, using a higher ISO, such as ISO 800 or above, may be necessary for night photography to capture enough light and maintain proper exposure, but it may introduce more noise in the image. It’s recommended to test different ISO settings in the specific night photography conditions you’re shooting in to find the optimal balance between sensitivity and image quality for your specific camera and situation.