In Search Of: Understanding ISO & How To Use It

ISO is one of the three pillars of photography (the other two being shutter speed and aperture), and it has a major impact on your images, such as noise or better known as grain. How does camera ISO affect your images? In this article, I will introduce ISO for beginners and explain how to use it effectively for the best possible results.

An example of with no grain/noise vs a lot of grain/noise

ISO is one of the most fundamental and essential aspects of photography, essential for primary camera control. Without a proper ISO setting, your camera will take photos that are either too bright or too dark.

But, first…

What does ISO stand for?

ISO stands for International Organization of Standardization.  The International Organization of Standardization was a governing body responsible for standardizing sensitivity ratings for camera sensors. In the days of film cameras, the ISO body would rate film’s sensitivity to light, giving it a speed and ASA rating. The light-sensitive film requires less light to develop a properly exposed photo. A high ISO number makes the roll of film more sensitive to light.

In very basic terms, ISO is simply a camera setting that will brighten or darken a photo. As you increase your ISO number, your photos will grow progressively brighter. For that reason, ISO can help you capture images in darker environments, or be more flexible about your aperture and shutter speed settings.

However, raising your ISO has consequences…

Why is ISO important?

A photo taken at too high of an ISO will show a lot of grain, also known as noise in the photography world, and might not be usable. So, brightening a photo via ISO is always a trade-off. You should only raise your ISO when you are unable to brighten the photo via shutter speed or aperture instead (for example, if using a longer shutter speed would cause your subject to be blurry). It’s important to note that newer cameras are capable of handling extremely high ISO’s and minimizing the negative impact.

Remember ISO value and exposure value are not the same thing. While ISO values control the light sensitivity, it doesn’t determine how much light is captured by the camera. That task belongs to the combined settings of your camera’s shutter speed & aperture.

ISO values does not influence exposure. Exposure value is the product of aperture and shutter speed, which together, capture a certain quantity of light in a given lighting situation. The base ISO number does influence the final image quality by controlling how bright or dark it will be, using the exposure value as a base.

Let’s talk about real world use…

How Do I Use ISO Practically?

Let’s use the example of you photographing a child in a dimly lit room. Imagine that you have set an exposure value of f/5.6 and 1/100 sec. Your base ISO number is set to 100, and considering that the room is poorly lit, the exposure will be very dark. You might get a little bit of an image, but nothing you can use. So you would try to increase the base ISO number to ISO 400, and that will make the exposure immediately improve even though the amount of light captured by the camera did not change.

You can increase the ISO much higher and still use the final product than you can decrease the shutter speed because at a certain point, no matter how steady your hands are, you will get some shake in the camera causing the image to be blurry. The typical person can freehand a camera to about 1/60 of a second and would require the stability of a tripod after that. If you’re moving around and taking pictures you could never lower your shutter speed to that unless you’re using external lighting, which I will explain in another article, that will freeze the image but capture some motion.

Today’s digital camera has several levels of sensor sensitivity, typically between ISO 100 and ISO 1600, and upwards . Many digital cameras offer high ISO settings (e.g. ISO 1600, ISO 2000, ISO 3200, even up to ISO 12,000!) This gives you the freedom to change the light sensitivity according to your needs. The signal received by the sensor is amplified using an analog process. There is a limit to how much this signal can be amplified before an image becomes too grainy to use.

How Do I Change My ISO?

Changing ISO varies from camera to camera. Here are some common ways to change ISO:

  • To start, enter a mode that lets you select the ISO yourself. Get out of Auto mode, and go to Manual, Shutter Priority, Aperture Priority, or Program (we tend to prefer Aperture Priority or Manual).
  • For entry-level DSLRs and mirrorless cameras, you probably need to open a menu (possibly the “quick menu”) and find the section for ISO. Select the value you want, or set it to Auto.
  • For higher-end cameras, there may be a dedicated “ISO” button on the camera. Press it while spinning one of the wheels to change your ISO setting. If you don’t see a button labeled “ISO”, it is still possible that your camera will let you program one to perform this task.
  • Other cameras may have a dedicated wheel that already has various ISO settings marked. This makes things even easier.

Check your camera manual if you still aren’t sure. However, it is worth being very familiar with how to change your ISO setting quickly, since it’s something you will likely be adjusting quite often, especially if you shoot in low light conditions without a tripod or external lighting.

Please comment or contact me if you have any further questions!


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