How a Digital Camera Works

How a digital camera works
This will not be enough detail to satisfy the physics majors out there, but it is detailed enough to help the practical Sports Photographer understand the basics of how a digital camera works.  Those old enough to remember film cameras know that a film camera worked by exposing film (photosensitive chemical) to light or a scene.  The aperture and shutter speed controlled the amount of light allowed to expose the film.  It was a chemical and mechanical process not requiring electrical power of any sort.  In today’s world of digital, it’s hard to imagine a camera without batteries.  Many of the basic photography concepts have remained the same in today’s digital world, but much has changed with digital cameras.

Digital Cameras
Instead of film, digital cameras are equipped with two critical devices, an image sensor and a chip/processor.  There are different types of image sensors such as CCD, CMOS or foveon.  The most common is the CCD which stands for charged-coupled device.  The chip/processor just like the one in your computer is a specialized computer that converts the captured light into digital numbers that represent your image and allows it to be written on a memory card in your camera and then transferred to your computer. 

The Image Sensor
The image sensor is a special solid-state device.  This device is covered with millions of light collecting diodes that electronically detect the brightness of the light.  These diodes or pixels laid across the image sensor represent the number of pixels the camera will shoot and that your photo will have.  When light strikes the sensor each diode/pixel collects a charge that leaves an imprint/picture on the pixel.  This charge in each pixel represents the brightness of that spot in the photo.  The brighter the light the higher the charge in that pixel and the less light the lower the charge.  Along with the brightness a special filtering process allows each pixel to also represent the appropriate color.  After the shutter closes and the exposure is complete the charges in each pixel are measured and converted to a digital number.  The digital number is represented by 1s and 0s which allows your image to then be saved on a memory card.  So in simplest terms the image sensor turns light into an electrical charge that is ultimately represented by digital 1s and 0s.

Controlling the Light
Just as with a conventional camera the lens controls the amount of light that reaches the sensor or CCD.  The amount of light is controlled through the aperture and shutter speed.  Aperture is how large the opening is that allows the light to strike the image sensor and shutter speed is the length of time that light is allowed to pass through the aperture.  Both the aperture and the shutter speed can be controlled by you, but can also be controlled automatically by the camera.  These two features work together to allow the proper amount of light to reach the sensor for an accurately exposed image, also stated as an accurate exposure of the sensor.

The Processor
The chip or processor in your camera is much like the processor in your computer.  The difference is it is designed and programmed to do very specific tasks. Those tasks are related to the processing of your image on your camera and includes the converting of the electrical charges to digital 1s and 0s.  In many ways you can think of your camera as a small computer.  The small LCD display is the computer screen and instead of a keyboard and mouse you have a menu system, dials and buttons. 

Familiarizing yourself with some of these basics will provide a foundation as you continue your understanding of digital photography,

ProPix Photography
The Sports Photographers

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