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ISO settings adjust the camera's sensitivity to light, striking a delicate balance between brightness and the risk of introducing grain, enabling photographers to adapt to any lighting condition...

What is ISO?

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

ISO Sensitivity is a standard set by the International Organization for Standardization (ISO). 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.

Exposure triangle.
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

Shutter speed, on the other hand, determines the length of time that the camera's sensor is exposed to light.

Exposure triangle

All three components make up the exposure triangle and 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 acts 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, you may need to use a wider aperture such as f/1.8 or f/2.4.

You may also need to use a longer shutter speed, such as under 1/100, to allow more light to enter the camera, but this could result in a blurred image:

Graphic of a low light situation with ISO.
Low-light situation with ISO

In this case, increasing the ISO (and potentially increasing shutter speed) could help achieve a properly exposed photo without sacrificing image quality:

Graphic of a low light situation with ISO that isn't blurry.
Low-light situation with ISO - not blurry

Conversely: In a bright outdoor situation, 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:

Graphic of a bright situation with ISO for an overexposed image.
Bright situation with ISO - overexposed

In this case, lowering the ISO could help prevent overexposure and maintain image quality:

Graphic of a bright situation with ISO for a properly exposed image.
Bright situation with ISO - properly exposed

Here's the bottom line: It's important to understand that changing the ISO can affect the exposure of the image. However, ISO can also impact the image quality and noise levels, which I'll touch on later.

Therefore, finding the right balance between ISO, aperture, and shutter speed is crucial to achieving the desired exposure while maintaining good image quality.

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.

This allows your camera to capture more light and produce a brighter image. Lowering the ISO number makes the camera sensor less sensitive to light, resulting in a darker image.

In short: Let's say you are photographing in a situation where there is not much light. Increasing the ISO can be beneficial to capture a properly exposed image without relying on a longer shutter speed or wider aperture:

Graphic of increasing ISO.
Increasing ISO

Let's say 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.

Graphic of decreasing ISO.
Decreasing 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.

I soon realized that higher ISO settings can introduce unwanted noise or grain in photos, resulting in decreased image quality:

Man wearing suit in a no noise photo.
Low ISO (No grain/noise)
DJ in a bar.
High ISO (High grain/noise)

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:

Low ISO image in a party.
Low ISO at night creating underexposed image

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. This way, when you're out on a photo shoot, you have a general idea of what ISO to use without getting grain or noise.

Here's the bottom line: 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...

You either need to get a better camera that handles higher ISOs 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 discussed noise or grain, which is a byproduct of taking an image with a very high ISO, but I wanted to explore it a bit more.

The presence of noise or grain in an image can be a creative choice or a distraction. This depends 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:

Intentional grain added to a beach photo under the pier.
Intentional noise or grain added

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 to further explore your 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, 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.

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:


Low ISO values typically range from ISO 100-400. You will usually use low ISO values when you are in a well-lit situation, such as outdoors during the day or in an indoor or studio setting with 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:

Low ISO in backyard.
Low ISO day time

Moderate ISO

Moderate ISO values typically range from ISO 400-1600. 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:

Moderate ISO in an indoor image.
Moderate ISO indoors

If you are outside, you will most likely need to use moderate ISO values at dusk or dawn. 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 photographing a fast-moving subject. Such as someone sprinting, a car, or an animal - where a higher sensitivity to light is needed:

Very high ISO photo in an indoor dark room.
Very high ISO indoor dark room

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 what ISO to use based on your current shooting situation.

1. Assess the available lighting

The first step in determining 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, 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:

Man wearing suit in a no noise photo.
Low ISO (No grain/noise)
DJ in a bar.
High ISO (High grain/noise)

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, 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 just to experiment and practice, then go for it. 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 figuring 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 might call for a higher ISO value:

Image of water fountain with blurred water and freeze framed photo.
Freezing the frame might need high ISO

On the other hand, if you are photographing a subject that is not moving, such as 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 figuring 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 you must test and experiment with your camera to understand its ISO performance in terms of boundaries:

Graphic with instructions on how to test and experiment with ISO.
Test and experiment ISO

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 knowing what ISO to use is to practice, practice, practice.

You see, 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 experience, you will develop a better understanding of your camera's ISO performance and the 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:

Three images showing low, moderate, and high ISOs.
Low, moderate, and high ISOs

Overall, these five steps can be considered a loop that considers the current lighting situation, desired image quality, and subject. 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.

Overtime, your photographic eye and knowledge of your camera's ISO values will allow you to walk into a scene and be able to know 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:

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.

When using ISO, it's important to check and use your camera's light meter. This will ensure proper exposure.

4. Consider a tripod or image stabilization

The fourth tip when using ISO is to consider a tripod or propping your camera on something for stability. You will find this useful 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.

Stabilization will also allow you to lower the shutter speed if 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 your images contain noise or grain, consider using noise reduction techniques in post-production. There are various post-processing software and tools for you to use.

For example: Adobe Photoshop and Lightroom have built-in tools to reduce noise in images, which I'll discuss a bit more later.

ISO in digital photography

ISO in digital photography is what most of this guide covers.

To recap: ISO in digital photography refers to the sensitivity of the camera's image sensor to light.

It 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 the 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 by the film itself.

You see: Once a roll of film is loaded into the camera, its ISO 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. 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, they will be apparent in higher ISO levels, which we've already covered.

Here's the bottom line: 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.

Others 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 for achieving 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 add a vintage or gritty look to your images creatively. This can be particularly desired in street photography, urban landscapes, or moody portraits where you are going for a grainy aesthetic.

Intentional grain added to a beach photo under the pier.
Intentional noise or grain added

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).

3. Low ISO and slow shutter speed

If you are photographing something moving and want to capture the motion blur effect, such as a waterfall or light trail, 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.

Image of water fountain with blurred water and freeze framed photo.
Freezing the frame might need high ISO

In summary: ISO and the rest of the exposure triangle allow you to implement many unique and artistic choices, but these are my favorites. I recommend playing around with the different combinations to find what interests you creatively.

ISO in post-production

In some cases, a higher ISO setting may cause noise or grain in your photos.

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 those from the Adobe Suite, such as 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 remove, 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 the Sharpening Tools, you can apply selective sharpening to the areas that need it to help restore some detail and clarity.

3. Localized adjustment tools

Many photo editing software have localized adjustment tools in the form of brushes or masks. You don't have to take a blanket approach to the noise reduction tool and use it on the whole image.

You can selectively apply adjustments to the specific areas of the image. You can 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.

In conclusion, I hope you took away something valuable from the guide on ISO in photography. The best way to learn ISO is just to 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!

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