How Does a DSLR Camera Work?

By Shawn McClain

DSLR cameras use a special kind of shutter.
i Jupiterimages/ Images

A digital single-lens reflex camera, or DSLR, is a combination of two different camera technologies. First, the single-lens reflex technology determines how the shutter operates to allow light through the lens and onto the sensor. Second, the digital aspect of the camera means that the camera uses a digital sensor to capture the image instead of a piece of film.

Capturing Light

Like all cameras, a DSLR works by manipulating light. When light bounces off the subject and makes its way to the observer, where the camera is located, if the light passes through a small enough opening it can create an image on the other side of the opening. By using a lens, positioned in front of the opening, the camera operator can bring that image into focus at a given distance behind the opening, which is where the DSLR's digital image sensor is located.

Single-Lens Reflex

The SLR aspect of the DSLR solves an old camera problem where the photographer's view of the subject was not the same as the camera's. When the shutter is closed, no light is getting through to the sensor, so the operator has to view the subject through a viewfinder, which may have a slightly different view of the subject. In an SLR camera, a mirror sits in front of the sensor or film, and light passing through the lens is reflected up into a prism and out into the viewfinder. When you press the shutter button, the mirror flips up out of the way and the two curtains that make up the shutter slide out of the way, allowing light to pass through and strike the sensor, creating the image.

The Digital Sensor

The digital sensor that captures the image separates DSLRs from old SLR film-based cameras. The sensor is made up of millions of photosites, which are also often called pixels, that are sensitive to light. When light strikes the sensor the individual photons are directed into the photosites where they are absorbed. The material in the photosite then releases an electron, creating an electrical charge. Once the image capturing is done, the power of the resulting charge from each photosite is relative to the number of photons that struck the sensor, and thus signifies the intensity of the light in that area of the image. This information is then fed into a processor, which creates the image that you see on the display. The digital sensor's photosites are arranged to capture red, green and blue light, as more than 16 million visible colors can be recreated using a mixture of these three colors.

DSLR Advantages

The digital aspect of DLSRs is one of their largest benefits, as you don't have to deal with physical film. This makes storing, moving and copying images so much easier. It also means that your images are stored on a memory card, which can be large enough to allow you to capture and store thousands of images. The mechanics of DSLRs also make them ideal when shooting speed is important. You can bring a DSLR into focus and snap the shot in a fraction of the time it would take a standard digital camera to do the same process. Because DSLRs require the use of a physical lens, they also allow you to change lenses to suit your needs. So you can use the same DSLR camera for telephoto shots and wide-angle landscapes, all by just quickly swapping out the lens.