Photography is a balancing act. Every photograph that has ever been taken has been done so through a combination of ISO, aperture, and shutter speed, which together is called the “Exposure Triangle”. These three components work to control the amount of light entering your camera, and is what ultimately delivers your image. This article will be looking at ISO, aperture, and shutter speed, as a way of better understanding how to use these instruments of the camera to your benefit.
To lay the groundwork of the Exposure Triangle, we’ll be going through an introduction of each area and some example images to better illustrate the possibilities of each setting.
ISO is a setting that alters your camera’s sensitivity to light. In analog photography, ISO is represented as film speeds, whereas in digital photography, it is a setting built within the camera. ISO measured in numbers ranging from 100 to 6400, although some cameras can go much lower or higher than that. The lower your ISO number (ISO 100, ISO 200), the less sensitive your camera is to light. On the other hand, the higher the number (ISO 1600, ISO 3200), the more sensitive your camera becomes.
A high ISO (ISO 3200) would be used for low-lit environments such as an indoor gym, a theatre performance, or a street at night. If you’re out shooting on a bright sunny day and have much available light to work with, a low ISO (ISO 100) is appropriate to use.
It is important to note, however, that the higher your ISO, the higher the amount of “grain” or “noise” will be present in the image. The opposite can be said for low ISO settings, resulting in “cleaner” images with very little to no noise present.
Shutter speed can be referred to as the “doorway” to let light into the camera. Think of it as an eyelid, opening and closing to record an image onto the camera’s sensor or negative. Shutter speeds are measured in fractions of a second, such as 1/250, 1/30, and ½. The shutter can also be held open for longer amounts of time, like 3 seconds or even 30 seconds, and this is most often used to capture motion in a long exposure.
It is important to understand that, the longer the shutter is held open, the more light is recorded into the camera. As the shutter is kept open for a significant amount of time, any motion that is recorded in the frame will have a “ghostly” effect, like blurs of pedestrians walking on the street or streams of lights from moving cars. This can create some pretty stylistic results, assuming that the camera has been placed on a tripod.
On the other hand, the quicker the shutter is, the less light is recorded into the camera. This means that any motion within the frame will be captured quite quickly, so the result is most often a “freeze-frame” capture, like an action shot of a basketball game or a photo of a single droplet of water. This use of shutter speed is often used for documentary, sports, or event photography to achieve the sharpest, in-the-moment image.
A high school photography teacher once referred to this as the “donut hole” of the camera, and ever since then I can’t think of it as anything but that. The “donut hole” varies in size depending on the aperture’s setting, controlled by the lens. Much like the retina in our eyes shrinks and enlarges to adjust to the light in our environment, as does the camera’s aperture to adjust to your shooting conditions. In the conventional digital camera, the aperture is measured in f/stops, usually ranging from f/1.4 to f/45.
This is where it gets kind of backwards. The lower the number on the f/stop, the wider the lens opens up, allowing more light to enter into the camera. The higher the number on the f/stop, the smaller the lens is open, limiting the amount of light that is entering through the lens. A key factor here is that a wide aperture of f/2.8 is going to deliver that out-of-focus bokeh effect, as a wide aperture allows for a shallower depth of field. Naturally, a smaller aperture of f/32 is going to deepen that depth of field, and bring everything in your frame into focus.
Balancing the Exposure Triangle
Now that we have an understanding of each element of the Exposure Triangle, let’s run through a little exercise to illustrate what we mean by “balancing”. To start, we will be changing the “stops” in our camera, which means doubling or halving the amount of light we enter into the camera by adjusting our ISO, aperture, or shutter speed settings.
Let’s take a look at this still-life bedside table shot, shot at ISO 6400, f/16, and 1/60th shutter speed on a Nikon D610. As it stands now, the image has a significant amount of noise which could be improved.
As there is much available daylight, we can start by changing our ISO to 200. For the Nikon D610, this change is 5 stops darker than ISO 6400. Capturing the scene again with just this change would result in an underexposed picture. We need to brighten it up by changing either the aperture or shutter speed. In this case, opening up the aperture would work in our favor, as it will bring the plant out of focus and place more emphasis on the camera.
To do this, we will open up the aperture by 5 stops to match our shift from ISO 6400 to ISO 200. On the Nikon D610, 5 stops brighter than f/16 is f/2.8.
As you can see, the image’s exposure remains the same, but the photo has an overall softer look. This is due to the fact that we have decreased noise significantly, and blurred the background to put the camera front-and-centre.
And that is your introduction to the Exposure Triangle. There are many different ways we could have altered the settings for our still-life image, such as dipping into both the aperture and shutter speed, but that is for another time. This example illustrates the basic element of the Exposure Triangle, balance, and is sure to intrigue about the endless possibilities of image making.