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The Essential Guide to Understanding ISO in Photography

ISO dial on a digital camera

If you’re a photographer looking to improve your skills and take your photos to the next level, you’ve probably heard of ISO.

ISO in photography is one of the three fundamental settings, along with aperture and shutter speed, and it can significantly impact the quality of your images.

In this ultimate guide, we’ll look at what ISO is on a camera, how it works, and how to use ISO photography to create better photos.

What Is ISO in Photography?

I’m going to start with a little introduction to ISO in photography:

In photography, ISO is typically measured in numbers such as 100, 200, 400, 800, etc. 

The lower the ISO number, the less sensitive the camera sensor is to light and the finer the image grain or noise will be. Conversely, the higher the ISO number, the more sensitive the sensor is to light, and the more noticeable the image grain or noise will be.

Example of a photo with a grainy look

Photographers use ISO to adjust the exposure of their images – in the simplest of terms, how dark or light their image will be.

What Does ISO Stand For in Photography?

The meaning of ISO in photography comes from the International Organization for Standardization, a standard set in 1988 by the ISO to refer to the sensitivity of the film in a camera to light.

In 1974, they combined the best aspects of two older rating systems (DIN and ASA) to create the ISO standard for film. Since then, digital camera manufacturers have also adopted this standard.

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What Is ISO in Digital Photography?

In digital photography, ISO refers to the sensitivity of the camera’s image sensor to light. The higher the ISO setting, the more sensitive the sensor becomes, allowing you to capture photos in low-light conditions.

How to Use ISO in Photography?

The right ISO photography setting depends on the lighting conditions of your environment.

In bright daylight, you’ll want to use a lower camera ISO (around 100-200) to prevent overexposure and maintain sharpness.

To brighten the image, you must increase the ISO (800-3200) when confronted with low-light conditions. However, keep in mind that as you increase the ISO, you also increase the noise in the image.

Grainy photo

ISO and the Holy Trinity of Exposure

The importance of ISO in photography cannot be underestimated, as it can make or break a photo.

Camera ISO alone doesn’t change your photo, only when used with aperture and shutter speed. For instance, you can increase the ISO to achieve a faster shutter speed if you need to capture fast-moving objects.

Formula 1 car

On the other hand, if you want to capture a sense of motion, you can lower the ISO to use a slower shutter speed.

However, increasing the ISO can make your pictures look grainy or noisy, reducing the detail and color range. So, you should balance these trade-offs when adjusting your ISO.

In my personal opinion, it’s best to keep the camera ISO at the lowest native setting for the best picture quality and only adjust it when you’re confronted with low light or when wanting to achieve a creative effect.

Creative portrait of a young woman. Dark black portrait of a young woman

There are also ways around some of these rules:

For example, to keep your ISO low and freeze motion, you can use a tripod and increase your shutter speed. That way, your photo will turn out sharp.

Similarly, if you want to keep your ISO low in low-light conditions, you can use flash or LED lights to compensate for the lack of light AND get the sharpness you desire.

When Should You Use High ISO?

There are several scenarios where raising the camera ISO may be necessary. These include:

  • Sports photography – such as capturing fast-moving subjects in an indoor sports event
  • Shooting portraits in low-light conditions, like during the night
  • Photographing landscapes at night or taking astrophotography shots that require a fast shutter speed to freeze the stars
  • Photographing a landscape or a building without a tripod
  • When you need bokeh effect in your image
  • Taking photos at indoor events with little light.
    Capturing a dark concert

When Should You Use Low ISO?

  • When you’re photographing products or objects using artificial lighting.
  • When you shoot landscapes, your camera is stabilized on a tripod.
  • While taking portraits in natural light
  • If you’re documenting an event with ample natural light or flash assistance.
Portrait photo of a young male sitting next to the pool in Spain

For example, the above photo was taken during bright daylight using a Sony A7 III mirrorless camera with ISO set to 50, f/2.2, 1/640s.

What Is Base ISO?

Base ISO is essentially the native ISO of your camera.

Many cameras have a base ISO of 100, but there are exceptions. For example, some Nikons have a base ISO of 200, and Fujifilm x100v has a base ISO of 160.


Base ISO is the “sweet spot” of ISO adjustment. That means you’d have to keep your ISO to this base value to get the utmost image quality in your photo. This is generally considered as being best practice.

As you probably know, this is possible only if you shoot in broad daylight. You’d have to increase the camera ISO if:

  • the light is too low
  • you need to freeze motion and get a sharp image
  • you need an increased depth of field

On some cameras, you will notice “HI” and “LO” ISO photography settings that allow you to extend ISO.

Generally, it’s not a good idea to use them.

How to Use ISO Creatively?

You can use a lower or higher ISO creatively – to overexpose, underexpose, or add grain. But why would you want that?

Underexposing photos for creative photos

Why Use a Lower ISO?

You can use a lower or higher ISO creatively – to overexpose, underexpose, or add grain. But why would you want that?

To Preserve the Details

Intentionally underexposing by one or two stops can be beneficial, as it can preserve bright background details and prevent the overexposure of highlights. I think it’s much easier to recover shadows in post-production than highlights that cannot be retrieved once blown out.

Landscape photo with a blow out sky

For example, in the photo above, the upper part of the image (sky) is completely blown out. In this particular case, it won’t be possible to recover the data from the highlights in this photo.

However, in this particular case, it was done intentionally and the photo was exposed for the main subject in the center of the photo.

To Add Contrast and Eliminate Distractions

Underexposed creative photo with a cat and a lot of contrast shadows

Let me exemplify this by using this photo: imagine photographing a subject (in this case, a cat) near a window in a dark room.

You can do this by placing the subject in the brightest light, adjusting the exposure accordingly, and underexposing the dark shadows.

The result will be a high-contrast shot with blacked-out shadows that calls attention to the main character.

To Create a Silhouette Effect

Silhouettes can be used to emphasize the shape and outline of a subject and can be particularly effective when photographing people, animals, or objects with distinct and recognizable forms.

To create a silhouette, you typically want to place your subject against a bright background, such as a sunset or a bright sky. You can then underexpose the image by adjusting your camera’s settings, such as using a faster shutter speed or a smaller aperture. 

Example of a creative silhouette photo against a bright light

Why Use a Higher ISO?

To Create an Overexposed Image (“High-Key” Photography)

Some photographers purposely use a high ISO to create an overexposed image, especially when they want to capture a bright and airy atmosphere or create a dreamy or ethereal look in their photos.

This type of photography is most often used in genres such as fashion, beauty, portrait, and minimalist photography.

Example of a high-key portrait photo

To Achieve a Grainy Look

Some photographers use a high ISO to achieve that grainy look reminiscent of film photography.

This can be desirable in certain types of photography, such as street photography, where the grainy look can add to the atmosphere and mood of the photo.

Grainy look in a photo with high ISO

In Black & White Photography

You can also use high ISO intentionally in black & white photography, where the grainy look can add character and texture to the image. Black & white photography is often associated with high-contrast and grainy photos.

Example of a black and white photo with high ISO

Frequently Asked Questions

#1. How Does ISO Affect a Photo?

ISO affects a photo by controlling the camera sensor’s sensitivity to light.

The higher the ISO, the more sensitive the sensor is, leading to brighter images – but also more noise. Lower ISO values result in darker images but with less noise.

#2. What ISO to Use at Night?

Using a high ISO in night photography or other low-light situations is best because that allows the camera to capture more light and produce brighter photos. However, you can use a lower ISO by involving a tripod.

High ISO at night portrait photography

#3. Does High ISO Affect Sharpness?

Yes, high ISO values can affect the sharpness of an image by introducing noise, which can make the image look less sharp or detailed.

However, this can vary depending on the camera and the conditions in which you took the photo. Using a tripod or image stabilization can help reduce the effect of camera shake and improve sharpness.

#4. Does ISO Affect Image Quality?

A higher ISO can reduce image quality. In comparison, a lower ISO will give better image quality, allowing more light to hit the sensor.

But high ISO allows for a faster shutter speed and a smaller aperture. It’s up to you to figure out which one you want to sacrifice to create your shoot.

#5. Why Is ISO Important in Photography?

It’s important to improve the art of setting up your camera ISO.

ISO is like a volume control for your camera’s sensitivity to light. Just like how turning up the volume on your speakers makes sounds louder, increasing the ISO makes your camera more sensitive to light, making the photo brighter.

Black and white photo of loud speakers

However, just like how increasing the volume can make the sound distorted, increasing the ISO too much can make the photo grainy and noisy. This is because when you increase the ISO, your camera amplifies the signal it receives from the sensor, and this amplification also amplifies any noise or imperfections in the signal.

The base ISO photography setting is like the default volume level on your speakers. It produces the cleanest signal with the least amount of noise. As you increase the ISO, the noise levels also increase, which can be noticeable in the form of grainy or speckled areas in the photo.

Additionally, increasing the ISO can also affect the dynamic range, which is the range of tones from the brightest to the darkest that a camera can capture. At low ISO settings, the camera can capture a broader range of tones, but as you increase the ISO, the dynamic range can decrease, which means that some details in the brightest or darkest parts of the photo may be lost.

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ISO Pro Tips

#1. Adjust Your ISO to Real-Life Situations

Different photography situations call for different camera ISO settings. For example, shooting scenic views in bright daylight might require a lower ISO setting, while taking action shots in low light conditions may require a higher ISO setting to freeze the motion. Indoor photography may require you to use at least an ISO of 1600 – if you’re not using a tripod.

Photographers also often have their preferred ISO settings for different situations, like a studio photographer who may use a standard ISO 100 setting or a street photographer who may pick ISO 800 for unpredictable lighting situations.

Alina Kareva taking photos of a kids game

#2. Don’t Be Afraid of High ISO

While I did say that using the native ISO is the best-case scenario, you shouldn’t avoid high ISOs when the situation calls for it. Nowadays, most professional cameras can reach an ISO of 1600 without significant noise.

When there’s absolutely no other way – like when you have to photograph a critical moment of a subject that is moving in low light conditions – the best deal is to go for it! That way, you still get the shot and avoid any blur that would come up if you were to lower your shutter speed. You can further smooth out the noise in the post-production.

If you’re having doubts, think of it like this: the alternative is missing the shot.

high iso photo

For example, the photo on the left was taken with ISO 2000, while the photo on the right was taken with ISO 8000.

What is ISO in Photography: Final Thoughts

The best ISO value depends on the lighting conditions, the “feel” you want to go for in your photos, and your other settings.

Remember that while the importance of ISO in photography is nothing to scoff at, it is just one part of the “holy trinity” of exposure. Aperture, shutter speed, and iso in photography all work together, and balancing these three elements is critical for achieving the perfect exposure and creating stunning photographs.

Lastly, remember never to stop learning and honing your skills in photography. If you feel like you have more questions than answers, I recommend reading our other blog posts here on OHMYCAMERA.


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Aleksandrs Karevs

Aleksandrs Karevs

Hi, my name is Aleksandrs and I am a full-stack digital marketer passionate about digital photography. In my free time, I enjoy taking photos with my everyday companion – FUJIFILM X100V. Read full story here.

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Aleksandrs Karevs OHMYCAMERA Founder & Author


Hi, my name is Aleksandr and I am a full-stack digital marketer from Riga, Latvia. In 2018 I became obsessed with photography and decided to create this blog to share my knowledge about both photography and marketing. In my free time, I enjoy taking photos with my everyday companion – FUJIFILM X100V.

Aleksandrs Karevs OHMYCAMERA Founder & Author


Hi, my name is Aleksandr and I am a full-stack digital marketer from Riga, Latvia. In 2018 I became obsessed with photography and decided to create this blog to share my knowledge about both photography and marketing. In my free time, I enjoy taking photos with my everyday companion – FUJIFILM X100V.

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Simply enter your email below to receive a FREE eBook filled with actionable tips for immediate photography improvements.