What Does ISO Stand for in Photography? Understanding ISO for Beginners

In Photography Basics by Stefano Caioni Leave a Comment

ISO in photography is a “rule of thumb” that is crucial to understand. Every photographer, whether professional or beginner, learns what ISO is and how to use it.

ISO is difficult to understand and if you want to know more about it, you’ve come to the right place.

Understanding what ISO is as a beginner photographer is key. ISO is one of the most important camera settings. Together, with aperture and shutter speed, it affects the exposure. It can create a significant change in the final look of your pictures.

So, what does ISO mean, and how to use it?

ISO determines how sensitive your camera sensor is to light. The darker the environment you’re shooting in, the higher the ISO needs to be. The correct amount of light, ensures you have the right exposure. ISO is one of the three main pillars of photography. It’s part of the exposure triangle together with aperture and shutter speed.

But ISO also has the drawback of introducing digital noise (grain) into your images. We’ll see how this works in this article and how to avoid it

ISO in Film Photography

What Does ISO Stand for in Photography?

What is ISO?

ISO stands for International Organization for Standardization. This non-governmental organization or corporation creates standards, certifications, and measurements. These “standards” give other individuals and organizations guidelines to follow in their industry.

ISO in Old Film Cameras

ISO became present (also known as ASA before) in old film cameras. Consider the thought of best practice. ISO is a measurement of the film speed. Based on the scenario in which a photographer is shooting in, an ISO “best practice” is useful.

Film cameras are a little more obsolete in modern-day photography. The introduction of DSLRs became a photographer’s favorite due to the automatic features. There are many benefits of DSLR’s which we will discuss shortly.

ISO photography

When shooting with film cameras, the photographer can only use ISO for 36 frames. The most common ISO is 100 to 400. The higher the “film speed”, the higher was the sensitivity of the film to light. The higher the sensitivity, the higher the film grain size. Grain isn’t an aspect of a photo that can be complementary.

If one is using a film camera indoors in low light, the ideal ISO is 400 to 1600. There is a huge difference in these numbers. Paying attention to how the photos turn out will help you determine what is best to use. Again “best practice!”

ISO in Modern Cameras

In modern digital cameras, ISO is an electronic emulation of the same effect. Both DSLRs and mirrorless cameras have this effect.

Instead of having to change film in your camera, you rotate a dial and select the different ISO numbers. Digital cameras have made the life of a photographer much smoother. For a beginner, digital cameras are a blessing as modern technology guides you.

ISO today is still referred to by many as changing the sensitivity of your sensor. This is not completely correct.

Yes, it is true ISO does affect the exposure triangle. It allows your camera to capture more or less light depending on its value. Still, it doesn’t change anything inside your camera from a mechanical perspective.

So what does ISO stand for in Photography?

For fun, let me try to give a more technical explanation of ISO.

Based on the internal mechanisms of a digital camera, we can say that cameras are smart machines. “ISO electronically amplifies the voltage observed at each pixel position before converting that voltage to a number. The effect of amplifying the gain of the photodetectors in the chip results in more grain in your image.”

It’s as if the light that hits the sensor is not pure, but amplified light. This sounds much more complicated than it is and you shouldn’t bother too much about it. But let’s accept that ISO doesn’t change anything in a “physical” sense. This is unlike the aperture and shutter speed in your camera.

To do a quick recap, the aperture is the stop that determines the brightness at an image point. What about the shutter speed? The basic answer is, this is the amount of time the shutter is open.

The shutter speed, aperture, and ISO that makes up the exposure triangle are essential in a photo. They may not always work in tandem but regardless, it is what makes a fabulous photo!

How ISO Works

ISO 200 on a camera

ISO is part of the exposure triangle, and it affects the brightness and darkness of your photos.

I want to make it easy for you to understand this concept.

You can imagine that ISO is a setting that works on its own. ISO does work as an independent element. Shutter speed and aperture are important, regardless.

Thanks to ISO, you can take photos in a dark environment and not have to worry. If you are in a very dark environment, a high ISO value allows you to create a brighter image. Setting your ISO to a high value allows the appropriate amount of light that hits the sensor. In contrast, with a low ISO value, you get a darker image.

ISO photography

ISO and the Exposure Triangle

To make sure we don’t oversimplify things, you must know what the exposure triangle is, and how ISO plays a part in it.

The Exposure Triangle

In photography, the exposure triangle represents the three elements of exposure. Remember we discussed that ISO can work alone? Shutter speed, aperture, and ISO do work as a team also. When increasing or decreasing one, it also requires the other two to adjust to create balance. Balance in your photos is the goal. That is what shows your true potential as a photographer.

Bringing balance, creativity, and beauty to your photos is what will draw people in. Don’t forget to bring your twist to your images. Show who you are. Give your audience a sense of “you” and why you love photography.

These elements, along with your personality are how your photos will stand out. For this reason, you have to make sure you don’t rely only on ISO to balance your exposure.

Check also:

ISO and Image Quality (Noise)

ISO photography

Do you have a good understanding of ISO now? Good! Now it’s time to learn how to use it to produce great photos and improve the quality of your images.

Let’s discuss digital noise and how ISO plays a role. What is digital noise? Simple definition, digital noise is image distortion. Digital noise can happen when there is brightness or color distortion in an image. If there isn’t a balance with how much light hits the sensor or ISO then this is where distortion comes in.

What do you do if you can’t achieve the exposure you want? Photography is a profession that takes time and experience. Experimentation, trial and error, and research are your resources.

Continue to experiment with ISO when the exposure isn’t where you want it. You should rely on ISO when you can’t achieve the exposure you want. If the image isn’t what you want, adjust the ISO. Also, consider the other elements of the exposure triangle (aperture and shutter speed).

In general, most people say that you should try to stick to the “base ISO” value to get the sharpest results.

Why do you fall back to the basics? High ISO values have the drawback of introducing digital noise (grain) in your images. Many factors can impact the quality of your image. The camera, size and quality of the sensor, and a high ISO can lead to reduced quality. of your image due to digital noise.


A few ways to reduce noise are:

  • Use a wider aperture and shoot at lower ISO
  • Use a slower shutter speed and shoot at lower ISO (might require a tripod)
  • Shoot in RAW. This allows you to capture more details in the scene and fix the image in Lightroom.
  • Use in-camera noise-reduction

Base ISO

The “Base ISO” or “Native ISO” is the unamplified sensitivity of the camera sensor.

The base ISO of a camera is the lowest value available. It represents the value in which you can secure an image with the highest quality and the least amount of noise.

The lower the ISO value you use, the better your image quality will be without the “noise.” Or at least the most minimal amount of noise.

  • Most cameras offer a base ISO of 100.
  • Micro Four Thirds cameras (e.g. Olympus and Panasonic) offer base ISO 200. 
  • Cameras such as the Nikon D810 or the newest D850 go down to ISO 64.

Pay attention, your camera might have a setting called extended ISO.

If you are a beginner, I recommend avoiding it. But if you want to learn more about it, this video by Tony Northrup can clarify its usage.

Tony is a high-class photographer best known for travel and nature photography. He has featured in TV shows, calendars, and many other publications around the world. His exceptional images will capture your attention.

What ISO Should You Use

Different environments, photography styles, and situations will require choosing a different ISO value.

Please note: consider the following as a more simple explanation of ISO values. Each style of photography would need a more in-depth discussion. This would help to highlight what contributes to delivering great image quality.


ISO in Landscape Photography

Landscape photography is a genre that I would recommend shooting at your camera’s base ISO. At the base ISO value, you’re not adding any gain, hence no digital noise. When shooting landscape photography, you should use the base ISO value whenever possible.

Shooting during the golden hour, you might need to increase your ISO to 400 or even 800 if shooting handheld. The light is less intense during this time and provides variations in lighting.If you using a tripod you can experiment with a long exposure technique. Keep your ISO to 100 and slow down the shutter speed.

Night Photo high ISO

ISO in Nighttime Photography

If you’re shooting the night sky, you’ll need to use a wide aperture. Producing a sharp image is possible in the dark. This is a case in which you can’t rely on only using ISO to get that sharp, clear photo.

Increasing the ISO to its max will degrade your image, then introduce noise. Long exposure is best. Slow shutter speed will make sure your camera captures enough light. Using reduced shutter speed will ensure you are not only relying only on ISO.

Night-time photography isn’t complicated, but it does take some time to master. One of the most important elements is ensuring you have enough light that enters the camera. Setting the ISO value between 400 and 800 is key.

The value does depend on if the night sky is visible in the camera. Once you confirm that the sky is visible (continue to increase if necessary), then you are ready to shoot. The correct amount of image exposure is important in this case. Learn the limits of your camera. Test shots are always a great way to understand how your camera is working, and what settings are best.

Last, note that a full-frame camera will give you the best results introducing less noise at high ISO. Another recommendation, use a tripod. This will prevent blur and stabilize the camera to give you those sharp, smooth images you want.

ISO photography

ISO in Portrait Photography

In portrait photography, you have to keep in mind that people are always on the move. Even when standing still for a photo, the human body is always in motion. Facial expressions change. Posture and poses change. If you are photographing kids, you better be ready at a moment’s notice. Kids are unpredictable and throw curveballs at any point!

For this reason, you need to use fast shutter speed to avoid introducing motion blur. Remember the exposure triangle described above? If you keep the aperture constant, the only way to get a fast shutter speed is to increase your ISO. Start from ISO 100, and depending on the light conditions, increase to ISO 400 and check the results.

Darker conditions will suggest a higher ISO or a proper light setting.


ISO in Street Photography

The ISO settings in street photography follow similar standards as portrait photography. To avoid motion blur, set your camera to aperture priority. Start from base ISO 100 or 200, and increase it as needed. Again, this all depends on the environment and light conditions.

It’s safe to say that in any situation where you plan to take photos, the camera settings will change.

Usually, narrow streets are darker even during the day. It’s best to start at ISO 400 in this case.

motion blur

You can also break the rule, get creative, and use motion blur as a feature of your photo. To add this touch, shoot in low light, and keep your ISO low. Shooting in aperture priority will increase the shutter speed. This technique will create motion blur in moving subjects.

I know, we discussed how to prevent motion blur, and why it’s not pleasing to the eye. Street photography is a whole new world. Motion blur adds depth and wonder to an otherwise simplistic scene.

ISO photography

ISO value for Wildlife Photography

As we’ve seen for street and portrait photography, your subjects will move. Animals are the most unpredictable and fascinating subjects.

Some of the best light is during the golden hour, and some wild animals tend to show up right at that time of the day! As you now know, if you don’t want motion blur, you need to increase your ISO and use fast shutter speed.

Start between ISO 400 and 800 and increase or decrease as needed. Finding the balance between motion blur and noise is instrumental.

Photographing wildlife is an incredible feat. Strength and vitality are two characteristics that shine through with balance and motion. Wildlife shots can be a once-in-a-lifetime chance to capture.

Think about being in the middle of the forest, quiet and pristine. Only the white noise of natural beauty and essence surrounds you. Birds flying above, animals roaming through the trees, and fresh air all around. What an amazing moment in time seen through the lens of your camera.

Read more about some ISO misconceptions in this great article by Nasim Mansurov.


Have fun experimenting with different ISO values. Get out in the field and see how the brightness of your image will change.

Remember to keep the correct balance in your exposure triangle.

Step out of your comfort zone and don’t be afraid to use your camera’s settings. Use your creativeness and love for photography to produce breathtaking images.

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