How do cameras work?

No matter the brand or price tag, cameras all work in roughly the same way. Understanding the simple mechanics of how cameras work will help you get the best possible results out of yours.

But before you head out to start taking photos, you need to understand the six essential elements involved in recording an image.

Understanding these requirements, regardless of whether you’re shooting on a DSLR, compact camera or iPhone, will make your photography so much better. These requirements are:

  • Light: Light is an essential part of any image, and it comes in many different types. How we use this light is important.
  • Subject: The subject of an image is the person, object or scene being photographed. The composition of an image should leave the viewer in no doubt about the subject.
  • Optics: This refers to lenses, which are used to focus the light and capture an image.
  • Aperture: Aperture controls the amount of light that reaches the recording medium in your camera. It also controls the depth of field (the range of sharpness range either side of the point of focus).
  • Time: Time relates to the shutter speed and how long the recording medium is exposed to light.
  • Medium: The recording medium is what records the image. This used to be film, but is now usually a CMOS or CCD chip.
    How cameras work diagram

      Once you understand these concepts and how they relate to one another, you can better start to understand how cameras work. 

      Let's look at these six key elements of photography in more detail.


      The central element of photography, light is what we use to create our images.
      © Karl Taylor

      To create a photograph, we can use two different types of light: natural and artificial. Natural light is sunlight, moonlight, or starlight, either direct or reflected. Artificial light is light from any other source, including lightbulbs, studio lights, or even candles.

      Light can be either hard or soft. This refers to the strength and density of the shadows created by the light. The harder the light, the darker and stronger the shadows.
      When we're taking photographs, it’s very important to think about and identify the type of light we’re using, as this will have a big impact on the final result.


      The thing being photographed.
      Photography subject

      Interested in fashion photography? Click here.

      Photography subject

      Interested in natural light portraits? Click here.

      The subject is the thing we’re photographing. It can be anything from a person to a product, a landscape to a llama!

      The subject relates closely to composition, which we’ll look at more closely later in this course. Composition refers to how we arrange, or compose, our subject matter within the frame of our image.


      Lenses allow us to focus light and capture an image.

      Camera lenses (or optics) focus light onto the recording medium. They control focal length, angle of view, and magnification, and help describe the image based on their particular characteristics.

      Lenses come in a variety of different focal lengths, ranging from ultra wide angle to super telephoto. Different lenses can produce very different results depending on the configurations within the lens barrel.
      Indoor portrait


      Controls the amount of light entering the camera, as well as the depth of field.

      Aperture refers to the size of the opening in the lens through which light passes before reaching the recording medium in your camera (sensor or film). 

      Aperture is measured in 'f-stops’. It is shown on your camera by the symbol ‘f’ (for example f1.2, f5.6 or f22). The lower the number, the larger the aperture (you can see this in the image below) and the more light reaches the recording medium. 
      By controlling the aperture, we can control not only the exposure level of an image, but also its depth of field (the sharpness range either side of the point of focus).
      Larger apertures, such as f2.8, allow the most light through the lens and result in a shallower depth of field. Smaller apertures like f22 allow less light through but have a greater depth of field.
      Aperture diagram


      Shutter speed determines how long it takes to capture an image.
      Shutter speed
      Shutter speed (also known as ‘exposure time’) determines how long the shutter remains open, allowing light to reach the sensor and causing an image to be recorded. 
      Shutter speed is in seconds (e.g. 1”, 10” or 30”) or fractions of a second (e.g. 1/10, 1/250 or 1/1000). The slower the shutter speed, the longer the shutter stays open and the more light is captured. Faster shutter speeds freeze movement, while slower shutter speeds allow for motion blur.
      Shutter speed diagram


      The recording medium records the image.
      Camera Sensors / Medium

      When light passes through the lens and reaches the recording medium, it records a photographic image.

      Historically, this medium was film. Today, most images are recorded onto digital sensors (though some photographers still like to use film). These sensors are mainly either CCD (charge-coupled device) or CMOS (complementary metal-oxide-semiconductor).

      The three most common sensor sizes are full-frame, crop (or APS-C) and medium format. Watch the video above to find out more.


      Whatever camera you’re using, understanding these six elements is essential to capturing photos you can be proud of.

      As this free course continues, we’ll be looking at each element in much greater detail.

      Before you move on to the next chapter, be sure to watch the video above to optimize your understanding.

      You can also download ‘An Introduction to Photography’, a FREE 90-page eBook, by clicking on the eBook icon below.

      WATCH NEXT: Class 2: Exposure in Photography

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