In photography “exposure” is defined as the amount of light falling per square metre on a camera sensor. To make things a lot less complicated, it is basically the amount of light that is reaching the camera sensor.  Exposure is amongst the first things that most photographers will have to learn and master in their careers. Photography literally means writing with light in Latin, hence why Exposure is a fundamental element of photography.

A camera essentially is a box of some kind. This box’s purpose is to capture light and record it. In the early days of photography, the light was recorded on film. Today, images are recorded on light-sensitive sensors. That, however, is a topic for another day. In order for a camera to record light, it must have some mechanism of letting light into it Then it must have a mechanism to expose the film or sensor to light for a certain period of time. That way light does not fall on the sensor or film for too long leaving the exposure bright white. These mechanisms of letting in light and exposing the sensor to light for periods of time are what are referred to as Exposure settings.

In order to understand how to capture an exposure or a photograph, one needs to understand exposure settings. Photographers need to understand what exposure settings do and what they affect in an image. An understanding of these settings will enable you as the photographer learn how to access light in different lighting situations and make appropriate changes to your exposure settings to capture a properly exposed photograph. In a later article, we will discuss in-depth what a properly exposed image is. There are three exposure settings. These three settings are Aperture, Shutter Speed and ISO.

Exposure Settings

Exposure settings describe the various mechanisms used to capture and adjust the amount of light that enters a camera system. Two of these settings directly affect the amount of light entering the camera while one does not directly affect the amount of light.

a) Aperture

Aperture refers to the hole through which light enters the camera to reach the camera sensor. The aperture is located in the lens that is mounted to the camera body. The aperture in most lens systems can be adjusted in size. Apertures can be increased in size to allow more light into a camera body or reduced in size to allow less light into the camera body. The aperture setting on a camera is indicated by an F-number. An example is f/1.8, f/11, f4.0, f/20.  

These F-numbers indicate the size of the hole in the lens. The F-numbers are essentially ratios. However, this is not an area I will get into at the moment as it can get really complicated. F-numbers as before stated indicate the size of the hole in the lens. However, it is important to note that smaller F-numbers indicate that the aperture is larger while larger F-numbers indicate that the aperture size is smaller. So as an example aperture f/4.0 is a much smaller aperture than f/1.8. This, therefore, means that at f/4.0 the image taken will be darker in exposure than an image taken at f/1.8. 

Other than the amount of light that enters the camera, the aperture also affects what is called Depth Of Field.  Depth of field refers to how much is seen in a scene. Larger aperture sizes (f/1.2, f/1.4, f/1.6, f/1.8) create a shallow depth of field. Shallow depth of field is characterized by a large amount of blur in an image. This effect is used mostly for portrait work. This is because this effect does a good job of isolating subjects from the background, helping viewers pay attention to the subject rather than the background. Smaller aperture sizes(f/5.6, f/6.3, f7.1, f/8.0), on the other hand, create a deep depth of field. Deep depth of field creates an effect where most of the scene in an image is in sharp focus. In such images, one can see all elements within an image from the foreground all the way into the background.

b) Shutter Speed

Shutter speed refers to the amount of time that the sensor is exposed to light coming into the camera. Cameras are built with a curtain called a Shutter that opens and closes exposing the camera sensor momentarily to light so as to record an image. The shutter speed is measured in seconds. Increasing the shutter speed exposes the camera sensor to less light as the shutter is open for a short period of time while decreasing the shutter speed exposes the camera sensor to more light as the shutter takes longer to open and close. Shutter speed is indicated by fractions of seconds or full seconds for example 30,15,0.3,1/10, 1/100, 1/250,1/8000.

Other than affecting the amount of light coming into the camera, shutter speed also affects motion within an image. Faster shutter speed is used to capture and freeze fast-moving subjects while a slower shutter speed creates a lot of motion in an image. Slow shutter speeds are used creatively to create images that simulate the effect of movement in them.

In modern-day cameras, the shutter is open and closed using a shutter button on the top right-hand side of the camera. The shutter can also be released using a remote shutter so as to take images from a distance or to take images of one’s self.

c) ISO

ISO  refers to the sensitivity of a camera’s sensor to light. ISO does not affect light directly. This means that ISO does not increase or decrease the amount of light coming into the camera. It only adjusts the sensitivity to available light on the sensor. ISO performance varies from camera to camera and comes in handy in low lighting situations. Low lighting situations are circumstances where the light is too little even for the camera to pick out with a large aperture or will probably require a very long shutter speed to achieve a proper exposure. ISO is indicated in incremental numbers example 100, 125,160,200… These values will be available based on the category of camera that you have access to.

In such low light circumstances, increasing the ISO increases the camera’s sensitivity so as to be able to capture the available light in a scene. ISO does not increase the amount of light coming into the camera. ISO adjusts the sensor’s sensitivity to the available light available in a scene. Increasing ISO increases the overall exposure while decreasing the ISO, decreases an image’s overall exposure.

There is, however, a drawback to using very high ISO in low light situations. Increasing the sensitivity to low light increases the amount of grain on the images that one takes. Grain is the physical embodiment of what is called interference within the sensor. Now if I get into that this article will become a little technical. So for easy understanding, have it at the back of your mind that as you increase your ISO, your images will get quite grainy. The more the grain, the lower the quality of the images that you produce. It is important to understand that you may not be able to eliminate grain entirely from your images. However, as a safeguard try to shoot at the lowest ISO possible based on the lighting situation you find yourself in.

Exposure settings are important to understand as you start your journey into photography. If you have already started or you are a professional, I am sure that the refresher course was not so bad, was it? The exposure settings help us photographers capture light. Understanding what each setting affects within an image helps us then start ‘writing with light’.