Even if you are new to photography, you have probably heard the term “ISO”. It is an incredibly useful and important setting in your camera that forms the exposure triangle along with aperture and shutter speed. Think of these three settings as the ingredients that allow you to capture a photo. Each one can be tweaked to give you a different outcome. But they are also linked so changing one will impact the others. In this quick guide to ISO in digital photography, you’ll learn what ISO is and why it is so important in digital photography?
What is ISO?
For anyone who began photography in the days of film, ISO (or ASA) was a film’s sensitivity to light. In other words the higher the ISO number of the film the more sensitive the film would be to light. So for example in low light conditions, you would use a higher ISO film to allow you to capture a photo. The reason that ISO is used is to standardize this sensitivity rating is so that you can shoot with different cameras and get a pretty close exposure value.
ISO in digital photography
In digital cameras, ISO basically means the same thing. But instead of film, it is the sensitivity of a sensor to light. Again, the higher your ISO is the more sensitive your sensor will be to light and thus allow to photograph in low light conditions.
The great thing about digital photography is that you are able to change the ISO whenever you want, even picture by picture. This feature is often taken for granted in digital photography and is one of the greatest benefits over using old analog cameras. If you are using film, you literally would have to change the film that was in your camera if you wanted a different ISO. Of course, you could only do this if the roll was finished so you were pretty much stuck with whatever you had in your camera for a while. Or you would have to carry around multiple cameras with different film in them. Sounds like a hassle and very expensive, right?
But with digital cameras you a have a whole range of ISO settings at your disposal. Most modern cameras will range from around 100 (or even 50 for some newer models) to 12,800 or even much greater.
The cost of raising your ISO?
Whilst it might be tempting to increase your ISO whenever you take a photo, it’s important that you understand the consequences of doing so. The higher that your ISO is the lower the quality of your image will be. This is because there will be more noise and grain in your photo which can mean the overall image will look soft. A lower ISO will not only mean a better quality image, but it will also mean a better dynamic range and better color as well.
But keep in mind that different cameras produce different levels of noise and grain at higher ISOs. So just because you can get an acceptable image with one at ISO 3200 doesn’t mean you will be able to with another one. The only way to know for sure is to test your camera out. Simply set up a shoot ideally on a tripod and photograph something at different ISO settings all the way to the maximum that your camera can take. Then zoom in to the photos in a post-processing software and check the result. This will give you a good indication of what you should expect. Don’t just rely on the LCD screen on the back of your camera. Even though an image might look fine on there, once zoomed in at a larger size you will notice the noise.
As a general rule, you should always keep your ISO as low as you are able to.
When to raise your ISO?
Even though raising your ISO comes at a price, there are times that you simply can not take the photo without doing so. The main reason that you often need to increase your ISO is to allow you to take the photo that you want to take at either the shutter speed that you need to (if there isn’t enough light) or at smaller apertures. For example, if you are photographing someone indoors where there isn’t much light if you do not raise your ISO you may not be able to use a fast enough shutter speed to freeze the action. Or if you are photographing a landscape scene handheld you will want to have a greater depth of field. But selecting a small aperture to allow you to achieve this will mean slower shutter speed if you don’t raise your ISO which will mean your image will suffer from camera shake.
But sometimes even during the day, you may have to increase your ISO to be able to freeze the action. For example, if you are photographing something that is moving very fast like horses running or a car, you’ll need to have a very fast shutter speed. This might only be achieved by raising your ISO.
The good news is that cameras are getting better at reducing the amount of noise in photos at high ISO settings. There are also options in most post-processing software to allow you to reduce the amount of noise in a photo at the expense of some detail.
ISO is a key component of photography and is something that you will need to learn about and understand to be able to utilize effectively. Doing so will give you much greater control over the photo taking process and allow you to photograph situations that wouldn’t be able to otherwise. But the key to using ISO is to do so only as much as you need to. So if you can get away without having to raise your ISO, then do so. Like anything else in photography, the more you learn and practice the better you will become. So go ahead and play around with your ISO setting and see how it can impact your images. In the meantime, this quick guide to ISO should help you.
Photo credits: Kav Dadfar – All rights reserved. No usage without permission. Dreamstime.