The adjustable opening—or f-stop—of a lens determines how much light passes through the lens on its way to the film plane, or nowadays, to the surface of the camera’s imaging sensor. The wider the aperture is set, the shallower the depth of field will be in the resulting image.Wider apertures allow for selective focus, the ability to isolate your subject from background and foreground elements within the frame.
Aperture Priority
A metering mode in which the photographer sets the desired lens aperture (f-stop) and the camera in turn automatically sets the appropriate shutter speed to match the scene being recorded. Portrait photographers usually prefer wider apertures for shallower depth of field (DOF), while landscape photographers prefer smaller apertures, which bring more of the scene into sharper focus.
A distortion of image quality or color rendition in a photographic image caused by optical limitations of the lens used for image capture.
Adobe RGB (Adobe RGB 1998):A widely accepted color space that encompasses a wider range of color than the more commonly used sRGB color space. Adobe RGB is the preferred color space for images intended for prepress applications. For more on this subject, see the explora article, “A Guide to Printing Photographs.”
AF Servo

Also known as Continuous Focus, AF Servo is maintained by partially pressing the camera’s shutter release button, which enables you to maintain focus continuously on a moving subject as the subject moves within the frame. Shutter-response times are usually faster in AF Servo, since the subject is already in focus. For more on this subject, see the explora article, “Choosing Autofocus Modes.”

Anti-Shake (Image Stabilization)
Also known as Image Stabilization (IS), Vibration Reduction (VR), or simply image stabilization, anti-shake technology is a method of reducing the effects of camera movement on the photographic image.
The APS format is about half the size (23.6 x 15.8mm) of a standard 35mm frame (24 x 36mm) and has a 1.5x magnification factor (multiply the focal length x 1.5) for determining the 35mm equivalent focal length of lenses used on APS-C format cameras.
The ability of the camera and lens to keep the subject in focus during an exposure. Autofocus can be Continuous, meaning focus is maintained regardless of where it moves within the frame, or Single, meaning the point of focus is locked regardless of where the subject may move.
AWB (Auto White Balance)

An in-camera function that automatically adjusts the chromatic balance of the scene to a neutral setting, regardless of the color characteristics of the ambient light source.

Blown out
Bright areas in a photo that are overexposed are said to be blown out. They won’t hold any detail and will be bleached white.

Pronounced ‘boh-kay’, this term is derived from the Japanese word for ‘blur’ and is used to describe the aesthetic quality of the blur in out-of-focus areas of a picture. The faster the lens, and the more aperture blades it has, the smoother the blur tends to be.

Bracketing involves taking multiple images of the same scene, usually in 1/3, 1/2, or full-stop increments, to create a choice of exposure options. Many cameras offer the option of bracketing as a custom function.
Buffer Memory
A buffer memory is a temporary “holding area” for image data waiting to be processed in a camera.
Burst Rate
The number of consecutive images a digital camera can capture continuously before filling the memory buffer or memory card. To capture a burst of images, the camera must first be locked into “Burst” mode or “Continuous” mode.
Card Reader/Writer
A device that allows you to transfer data directly from a camera’s removable memory card to the computer, without being compelled to connect the camera to the computer.
Chromatic Aberration
Also known as color fringing, chromatic aberration occurs when the collective color wavelengths of an image fail to focus on a common plane. The results of chromatic aberration are most noticeable around the edges of high-contrast images, especially toward the edges of the frame.

This is what happens to the histogram when you grossly overexpose or underexpose a picture. In an overexposed shot, the histogram will usually be bunched up on the right and parts of it will be ‘clipped’ off by the edge of the graph. If the histogram is bunched up on the left and clipped by the opposite side of the graph, this usually indicates an underexposed photo.

CMY Color (Cyan, Magenta and Yellow)
These three secondary colors can be combined to recreate all other colors. Like CMYK, CMY is used in printing to create the colors seen in a print, although with less density in the blacks than CMYK color. CMY color is used in some of the least expensive desktop printers.
CMYK Color (Cyan, Magenta, Yellow, Black)
CMYK is the color space used for commercial offset printing. CMYK is also a common working color space for inkjet, laser, dye-sublimation, and wax thermal printers.CodecA codec is file format for recording video files. Popular codecs include H.264, MJPEG, MPEG-4 AVC/H.264 and AVCHD.
Color Calibration
A process by which the image source (digital camera or scanner), monitor and output (printer) are calibrated to use the same or similar color standard, i.e., Adobe RGB, sRGB, etc). This ensures that the image viewed on the monitor has the same range of colors as the image that is printed, and any adjustments made to the color of the image in the computer are accurately represented when the image is printed.
Color Depth
The number of distinct colors that can be represented by a piece of hardware or software. Color depth is sometimes referred to as “bit” depth because it is directly related to the number of bits used for each pixel.
Color Palette
A palette is the set of available colors.
Color Space
The range of colors that can be reproduced on a computer monitor or in print. The most commonly used color spaces for digital imaging are the baseline sRGB and wider-gamut Adobe RGB (1998).
CompactFlash Card (CF)
A popular flash memory device, which is available in a number of storage capacities. Unlike earlier mechanically driven MicroDrives, newer CF cards are solid state, quite stable, and are capable of operating under extreme environmental conditions.
Color Temperature
A linear scale for measuring the color of ambient light with warm (yellow) light measured in lower numbers and cool (blue) light measured in higher numbers.
Depth of Field (DOF)
Literally, the measure of how much of the background and foreground area before and beyond your subject is in focus. Depth of field can be increased by stopping the lens down to smaller apertures. Conversely, opening the lens to a wider aperture can narrow the depth of field. For more on this subject, see the explora article, “Depth of Field, Part I: The Basics.”
Depth of Focus
Depth of focus is the measurement of the area in focus within an image, from the closest point of focus to the furthest point of focus.
Digital Negative
Digital Negative (DNG) is a publically available raw image format owned by Adobe and used for digital photography. It’s based on the TIFF/EP standard format and incorporates the use of metadata.
DSLR (Digital Single Lens Reflex)
A single lens reflex (SLR) camera that captures digital images.
Dynamic Range
The range of brightness and tonality reproduced in a digital (or traditional) photographic image. Wider dynamic range translates into greater tonal values (and detail) between the darkest shadows and the brightest highlights. For more on this subject, see the explora article, “Dynamic Range Explained.”
DPI (Dots per Inch)
Printing term for resolution. Also referred to as ppi (pixels per inch) when describing monitor resolution. The higher the ppi/dpi, the higher the resolution of the resulting image will be.

Dust bunnies
In the wider world, dust bunnies are clumps of dust and fluff that you find drifting around wooden floors. In the camera world, dust bunnies are the annoying dots of sensor dust that show up in the same place in consecutive photos. These usually have to be removed manually (to find out how to do this, check out our safe guide to sensor cleaning).

Exposure is the phenomenon of light striking the surface of film or a digital imaging sensor. The exposure is determined by the volume of light passing through the lens aperture (f/stop) combined with the duration of the exposure (shutter speed).
F-Stop (Aperture)
A term used to describe the aperture, or diaphragm opening of a lens. F-stops are defined numerically:  f/1.4, f/5.6, f/22, etc. Larger, or wider apertures, allow more light to enter the lens, which calls for faster shutter speeds. “Faster” (wider) apertures also allow for selective focus (narrow depth of field), while slower (smaller) apertures allow for greater depth of field. Wider apertures are preferable for portraits, while smaller apertures are preferable for landscapes. For more on this subject, see the explora article, “Understanding Aperture.”
File Format
The way an image is saved to a digital camera’s memory.  JPEG, TIFF, and raw (DNG or other proprietary file formats) are the most common file formats found in digital cameras.
Software programs or data that have been written to read-only memory (ROM).
Flash Sync
Flash sync is used to describe either the connection point where you plug an external electronic flash into your camera (usually a PC port or the camera’s hot shoe), or the fastest shutter speed at which your camera can “sync” with an external flash. Most DSLRs have top sync speeds of 1/125th to 1/320th-second, although some camera/flash combinations can be synced at speeds of up to 1/15,000th-second. For more on this subject, see the explora article, “The B&H Speedlight Buyer’s Guide.”
Four Thirds (4/3)
A compact digital camera format designed around a 17.3 x 13mm imaging sensor, which is a quarter the size of a full-frame (35mm) imaging sensor.


As in ‘that’s a lovely piece of glass’. Glass is another term for lenses, generally used by photographers that understand that quality of a lens matters more than the quality of the camera attached to it.

A visual representation of the exposure values of a digital image. Histograms are most commonly illustrated in graph form by displaying the light values of the image’s shadows, midtones, and highlights as vertical peaks and valleys along a horizontal plane.
ISO (International Organization for Standardization)
Film speed rating expressed as a number indicating an image sensor’s (or film’s) sensitivity to light. The higher the number, the more sensitive and faster the sensor (or film) is.

A common file format for digital photographs. While most now know what this photography term is, many still don’t know that it gets its name from the Joint Photographic Experts Group that developed it, and that the JPEG file format allows files of colour photos to be compressed to a smaller digital file than if the full range of colours were to be saved.

Light bucket
Another term for a fast lens. Light bucket is also used to describe a photosite on a digital camera sensor (the element that ‘captures’ the light to make an exposure).