The exposure triangle is the basis of any exposure. In order to create the desired photograph you need to determine a value for each side of the triangle. As the name suggests, the exposure triangle is made up of three values (or sides). This article is one of four articles that will break down each side to help you understand each component of the triangle.
Before we get started let’s cover off some of the terminology so that we have a base that we all understand.
In the exposure triangle, APERTURE refers to the F-Stop value. That is, how open is your lens. The SHUTTER refers to how long that shutter is open and exposing the sensor to the light coming in from the scene.
So when it comes to photography what is ISO?
ISO stands for International Standards Organization and in photography, it refers to the sensitivity of the sensor.
So now that we know that ISO refers to the sensitivity setting of your sensor, let’s dive into what this actually means. Adjusting the sensitivity of your sensor is not a new thing. Back in the film days, you were able to buy film that was referred to as fast film. This film was very sensitive to light enable to capture scenes that were very dark. 3200 speed film was considered some of the fastest films available. Nowadays, just about everyone uses digital cameras. The advancement of digital camera technology, in particularly the sensor, have allowed cameras to shoot within ISO value which is much higher than what we were able to get back in the film days.
ISO values can range from 50 up to 104,000 and beyond. The smaller the value the less light sensitive the sensor is. The higher the value, the more sensitive the sensor. To anyone that has not used ISO before it might seem strange to want to change the value of the ISO setting on your camera. Why would you not just set the camera to a value and just leave it there? In fact, ISO seems like a bit of a super power when you think about it. Let’s set it to the maximum and leave it there for ever. Well, it turns out that making the sensor more sensitive to light also has some negative effects that you need to counter. Let me explain.
In order to demonstrate this, I’m going to describe a scene for you that should illustrate this point. Imagine you are in a city park. You are there to record the chirping of birds. You set up your microphone but the birds are not very loud so your recording is not picking up the sounds of the birds. So you turn up the microphone recording volume to maximum. You make your new recording but you now realise that not only can you hear the birds, but you can also hear the far away traffic from a few blocks away. You can also hear the plane that was flying overhead. You then have to reduce the level of your microphone so that you only pick up the sound of the birds without the sound of traffic or any planes flying by. Setting the ISO in your camera works pretty much the same way. When you set your ISO too high, you will start to pick up rouge photons (light particles) that are bouncing around. This results in something called noise. You have probably seen noise if you’ve ever taken a photograph in a dark area using your phone. It looks like random pixels of mixed colors sprinkled all over the top of your photo. In film cameras this was caused by the grain of the film which at times, could add something pleasant to the photograph. Digital cameras are not so forgiving when it comes to noise so most of the time it does not look good.
Below is a sample of an image with noise. See the dark areas and the random pixels.
Much like the microphone example, we have to use ISO sparingly. Raise it only to the level that allows you to capture the image and no more. ISO is of course, only one of the parameters of the triangle and so we might have to compensate using either APERTURE or SHUTTER SPEED but we will get into that in the final article that talks about bringing them all together to make a photo.
Of course, it might be that the only way to capture the photo is by cranking up the ISO as high as it goes. Yes, the picture will be grainy but at least you have the photo. There are some tools that you can use to try to reduce the effect of a high ISO during the editing process but these tools have limitations so it is always best to start off with the cleanest photo first.
CONCLUSION
So what should my ISO be set at? There is no one answer to this of course. It really depends on your situation at the time. My method to setting up my ISO is always the same. I start off at the lowest setting and see what my other exposure settings tell me. If it’s going to be too slow to hand hold the camera and, I can only change my ISO, I will raise it to the point where it lets me take the photo and no more.
Realistically speaking, if you have a camera that was built on or after 2015, you will probably be able to raise the ISO to 800 or maybe even 1600 and notice almost no difference. Most of the advances in camera technology is around the ISO and dynamic range. If your camera is older it just means that you are going to have to be a little more careful and pay more attention. Then again, ISO is just one of the parameters here, and as they say, there are more than one way to skin a cat. Figuratively speaking of course. I love my cat!
Dan Cantero