- A photograph taken with a digital single lens reflex (DSLR) camera starts at the lens. A DSLR lens is really a collection of sub-lenses called elements. Each lens refines and focuses light to create a sharp, high quality image. Lenses on DSLRs can be changed for different purposes. Wide angle lenses can be attached for landscapes. Long telephoto lenses can be used for wildlife or sports photography. Zoom lenses, or lenses that change their focal length between wide-angle and telephoto, are very common and are often included with the camera.
- What makes a DSLR unique is the mirror and pentaprism. A mirror behind the lens reflects the light upward to a 5-sided prism, or pentaprism, where it is reflected through the viewfinder. When the shutter release is pressed, the mirror just behind the lens flips up to allow a straight path between the light and the shutter. The shutter opens for the required time and the light falls on the sensor. In a DSLR what a photographer sees in the viewfinder is almost exactly what is captured by the sensor.
- In a DSLR, the shutter lies between the flip-up mirror and the sensor and the aperture is found in the lens. The aperture controls, by expanding and contracting, the amount of light passing through the lens. The shutter controls the amount of light falling on the sensor by remaining open for a specific amount of time. The shutter and aperture work together to allow a precise amount of light to fall on the sensor.
- The sensor is a matrix of tiny devices that measure the intensity and color of the light allowed to fall on the sensor by the shutter. These devices are called sensor sites and are comprised of a tiny lens, a signal amplifier, and an analog to digital converter. The quality of the final image is primarily a factor of sensor quality.
- After the image has been captured by the sensor and converted into a digital form, basic image processing is done in the camera. This could include removing noise and grain inherent in the sensor, adjusting color levels to user taste, and other simple tasks that don't require the power of a desktop computer. More modern DSLRs have more powerful computers that allow more complex in-camera processing like converting an image from color to black and white.
- After image processing, the image is stored on a flash memory card for later retrieval by computers. Flash memory is used because it doesn't require power to store an image. Common memory cards are xD, SD, MemoryStick and Compact Flash. Once an image is on a memory card, it can be read by any computer with an appropriate card reader. Most, but not all, DSLRs use Compact Flash or SD memory.
