What is Exposure in Photography


In photography, your exposure determines what gets recorded on your camera’s image sensor. The science behind exposure in photography is called Sensitometry.

Getting the right exposure is fundamental in photography. It’s like getting your balance in riding a bike. You’re never going to win a competition unless you have an awareness of your balance from the get-go.

Three camera settings will factor into your photography exposure: Aperture, Shutter Speed, and ISO. So the question then becomes, “ How do we achieve correct exposure “.

How to Control Exposure in Photography.

Between the lens and the camera’s sensor are three settings we use for image exposure control, to control the exact amount of light hitting the camera sensor. The three basic functions to control exposure settings are:

  • ISO
  • Shutter Speed
  • Aperture

This article will teach you the basics of these three settings that create the exposure triangle, as well as different techniques you can use to measure the exposure value. With this knowledge in mind, you’ll be able to expose your photos perfectly every time.


First, let’s look at ISO. ISO is a value that represents how sensitive the sensor in your camera is to the light passing through the camera lens and hitting the sensor. Each value of the ISO rating represents what is known as a “stop” of light.

Each ISO number represents a doubling (going up) or a halving (going down) of the sensor’s sensitivity to light.

The ISO can easily be changed in your camera in the menu settings or on a dial. Keep in mind that the higher the ISO setting, the more grainy your photos will appear. Depending on your lighting situation, you’ll want to adjust the ISO accordingly.

Shutter Speed

Your shutter speed is the speed at which your camera shutter (sometimes called the curtain) opens and closes. This duration determines how much light passes through the lens to reach the camera sensor.

Think of a shade pulled down on a window, and then quickly open it and close it. For an instant, the room was filled with light, and the length of time that burst of light filled the room was shutter speed! That is basically how a shutter controls the amount of light getting to the sensor. The time the shade was open determined – to some extent – how much light came into the room – but so did the size of the window! That window opening acted as the aperture explained below.

Shutter speeds are measured in seconds and fractions of seconds. Each shutter speed value also represents a “stop” of light.

If you’re hand-holding your camera, remember to set your shutter speed to at least 1/60th sec. Anything slower than that will cause your images to be blurry.


The aperture is built inside each lens and controls how much light enters the lens. Now for some clarification on shutter speeds. Looking at the photo below, you will see the changing numbers are the shutter speeds in fractions of a second (i.e., 30 = 1/30, 60 = 1/60). This is the time taken from when the shutter opens to when the shutter closes after you press the shutter release.

Moving from one speed to the next halves the amount of light that enters the camera. Moving the other way to a slow shutter speed doubles the amount of light that enters the camera. This change from one speed to another is called moving a stop. For instance, moving from a speed of 1/30th to 1/60th of a second is going 1 stop faster, and from 1/60th of a second to 1/250th of a second is moving 2 stops.

The aperture controls the volume of light that passes through the lens to hit the sensor. Aperture settings are measured in numbers, called f-numbers, or f-stops. Each f-number represents a stop of light.

An easy way to think of aperture is to compare it to the pupils in your eyes. The bigger the opening, the more light will come through, just like how your pupils function. It expands to allow more light in darker settings.

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