Glossary - Digital SLR and Mirrorless Cameras




Welcome to Digital SLR Camera

The terminology used within the digital SLR camera market can be difficult to grasp for both beginners and more advanced photographers. Digital SLR cameras are constantly evolving with new features being added at a rapid pace. A few years ago, a feature such as face detection was unheard of and now this feature can be found on many digital compacts as well as on a digital slr cameras.

This digital slr camera glossary will list most of the main terms used in digital slr photography and will expand over time to include new terms as they become more widely adopted. In many cases new terms are brought out to differentiate feature sets between manufacturers such as image stabilization. Nikon calls their system Vibration Reduction while Sony has Super Steadyshot. 

Auto Exposure
The camera sets both an appropriate aperture and shutter speed for current lighting conditions.

Auto Focus
Based on a variety of systems such as active autofocus or passive autofocus, the camera and lens will focus on a subject normally when the shutter is half pressed or fully pressed.

Aperture Priority
The user can manually set the aperture while the camera selects a suitable shutter speed for correct exposure. Aperture Priority is useful for many photographic situations such as determining the depth of field for landscape photography.

Barrel Distortion
In this situation, magnification decreases with distance from the optical axis. Commonly associated with wide angle lenses where the image appears partly spherical and curves outwards.

Bit
This is a Binary Digit and can either be one of two states - 0 or 1.

Bitmap
A raster image composed of an array of bits. A commonly used file format in digital imaging resulting in large file sizes as the image is uncompressed.

Bracketing
Taking multiple shots of the same scene with different exposure settings. Some cameras have an auto-bracketing option allowing 3 photographs to be taken at once with one image given more exposure than the standard image and one image given less for a darker image.

Buffer
Built in camera memory where images are stored before being written to the memory card. Some digital slr cameras have very large buffers allowing multiple shots to taken and saved quickly in both raw and jpeg file formats.

Byte
Binary unit composed of 8 bits. In computing, 1 kilobyte (1 kb) equals 1,024 bytes. 1 Megabyte (1 mb) equals 1,048,576 bytes and 1 Gigabyte (1 gb) equals 1,073,741,824 bytes.

CCD
Stands for Charge Coupled Device and is one type of chip or sensor used in a variety of digital cameras or digital SLR cameras and scanners. Converts light into a an electric charge and then into an electronic signal. CCDs or CMOS sensors (see below) for digital slr cameras come in a variety of sizes including:

4/3" - Four thirds system sensor measuring approximately 18mm x 13.5mm. Used mainly for Olympus & Panasonic digital SLRs. 

APS-C - Sensor measuring approximately 25mm x 16.7mm. Found in many Nikon, Canon & Pentax DSLR cameras. 

35mm - Full frame sensor measuring approximately 36mm x 24mm. Full frame CMOS sensors found in very expensive professional digital SLR cameras such as the Canon EOS-1Ds Mark III and Nikon D3.

CMOS
Stands for Complementary Metal Oxide Semiconductor. With advances in technology the differences between CCD and CMOS sensors are now very minimal. CMOS sensors are a type of integrated circuit and convert light into electrons. See table above for CMOS & CCS sensor sizes.

CompactFlash
Commonly used flash memory card which comes in two types - Type I measures 36.4 x 42.8 x 3.3mm and Type II is the same size but 5mm thick. Introduced by Sandisk in 1994, CompactFlash cards come in a variety of sizes and the larger CF2 format is also used by IBM's Microdrive which is a miniature hard disk.

Depth of Field
The area within a photograph from the nearest subject to the furthest subject which is relatively sharp according to the photographer. Depth of field (DOF) can vary according to aperture selection, lens type and distance from the main subject. In general, larger apertures such as f2.8 will give less depth of field than smaller apertures such as f8 or f11. Also, lenses with shorter focal lengths will give more depth of field than lenses with long focal lengths. For instance a 28mm wide angle lens will provide more DOF than a 100mm telephoto lens. Depth of field decreases with an increase in focal length. Finally, DOF increases as the distance from the subject is increased i.e. DOF will be higher when shooting a subject from 10 meters than say from 5 meters.

Digital Zoom
Beyond the optical zoom, the digital zoom enlarges the central portion of the image while maintaining the image aspect ratio and interpolating pixels to match the size of the original image. Digital zoom results in a significant loss of image quality and is best avoided whenever possible.

Dust Reduction
Many digital slr cameras now come with a facility to reduce or eliminate dust particles which may attach themselves to the CCD or image sensor when the user changes lenses leaving the inside of the digital slr camera exposed to outside dust and particles. Olympus pioneered dust reduction systems and modern Olympus digital slrs use a Supersonic Wave Filter which lies in front of the CCD and any dust captured is removed by ultrasonic activation.

DPI
DPI (Dots Per Inch) are a measurement unit used by output devices such as printers, scanners and monitors. Images which pack in more dots per inch tend to have higher resolutions and larges image file sizes. Monitors display images at 72 dpi while most printers will print professional quality images at 300 dpi but most images will also print perfectly well at lower dots per inch. Interpolating the dots per inch of an image using graphics software or scanner software usually results in a lowering of image quality.

Dye Sublimation Printer
Dye sublimation printers are capable of producing high quality images and use a technique involving heating dyes composed of CMYO colors onto paper, plastic and other materials. The more commonly used CMYK colors are replaced by CMYO with the black dye being replaced by a clear coating which protects the print from moisture and fading from UV light.

More terms from letters E to K to follow shortly.