The Photo Dictionary
Very often we see words and acronyms in photography so I hope this photography dictionary can explain and help a bit in deciphering the photo language. I will add more continuously over time. Any requests for words to add to the dictionary, contact me.
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.
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.
There are two types: On camera and on lens stabilisation. For example the Canon M50 has inbuilt IS.
The size of the opening in the lens. More Info.
A mode in which the photographer sets the lens aperture (f-stop) and the camera in turn automatically sets the appropriate shutter speed to match the environment.
Aspect ratio refers to the shape, or format, of the image produced by a camera.
The ability of the camera and lens to keep the subject in focus during an exposure. Autofocus can be Continuous, meaning the 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.
Average metering takes all of the light values for a given scene—highlights, shadows, and mid-tones—and averages them together to establish an overall exposure. Average metering is best used for front-lit subjects under average lighting conditions. Backlit subjects tend to be silhouetted when metered in average mode.
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.
A bit (binary digit) is the smallest unit of digital information. Eight bits equal one byte.
A method of storing digital information by mapping out an image bit by bit. The density of the pixels determines how sharp the image resolution will be. Most image files are bitmapped. Bitmap images are compatible with all types of computers.
Blowout is caused by overexposure, which results in a complete loss of highlight detail.
An English transliteration of a Japanese word that means “haze” or “blur.” Pronounced boh-Keh, it refers to the out-of-focus areas in a photograph with limited depth of field, particularly around, but not limited to, the highlight areas. Bokeh appears as little circles in the unsharp areas. Depending upon the shape of the opening formed by the blades of the lens’s aperture, the circles appear either more or less circular. More Info.
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. An advanced application of bracketing is HDR imaging (High Dynamic Range) in which several bracketed images are sampled in-camera and selectively combined into a single, optimized image file.
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.
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. Chromatic aberration is most common on less expensive lenses, although even the best optics can occasionally display lower levels of chromatic aberration, under certain conditions.
A method of reducing the size of a digital image file to free up the storage capacity of memory cards and hard drives. Compression technologies are distinguished from one another by whether or not they remove detail and color from the image. Lossless technologies compress image data without removing detail, while “lossy” technologies compress images by removing some detail. Joint Photographic Experts Group (JPEG) is a lossy compression format supported by JPEG, PDF and PostScript language file formats. Most video formats are also lossy formats. TIFF files are not and, as such, are far more stable than JPEGs and other lossy file formats.
The depth of Field (DOF)
Literally, the measure of how much of the background and foreground area before and beyond your subject is in focus. The 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. More Info.
DSLR (Digital Single Lens Reflex)
A single lens reflex (SLR) camera that captures digital images. Canon Cameras.
Dye-sublimation printers, or “dye-sub” printers, are a type of digital photo printer. Unlike inkjet printers, which spray fine droplets of ink on the print surface, dye-sub printers employ a cellophane ribbon that momentarily vaporizes when heated to extremely high temperatures, while being transferred to the print surface.
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.
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. For viewing images at magnifications of up to life size on a computer screen, you only need 72 dpi. For offset printing, the image must be set to 300 dpi at the desired print size, and for inkjet prints, anywhere from 180 to 360 dpi at the desired print size, preferably with a number divisible by 3. Dpi settings above 400 can diminish the quality of inkjet output.
An electronic viewfinder digitally replicates the field of view of the area captured by the camera lens. While once considered a poor replacement for optical viewfinders, newer EVFs containing million-plus pixels and faster refresh times have become quite accurate, in many cases approaching the clarity levels of optical finders. An advantage of EVFs is their ability to display exposure data and grids on demand.
Exposure is the phenomenon of light striking the surface of a 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). More Info.
Adding to or subtracting from the “correct” exposure time indicated by the camera’s light meter, which results in a final exposure that is either lighter or darker than the recommended exposure time. Most cameras allow for exposure compensation in 1/2, 1/3, or full-stop increments. Note that the “correct” exposure is not necessarily the “best” exposure.
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. More Info.
Graphics Interface designed by CompuServe for using images online. This is a 256-color or 8-bit image.
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, mid-tones, and highlights as vertical peaks and valleys along a horizontal plane. When viewing a histogram, the shadows are represented on the left side of the graph, highlights on the right side, and mid-tones in the central portion of the graph.
ICC Profile (International Color Consortium profile)
A universally recognized color-management standard for specifying the color attributes of digital imaging devices (scanners, digital cameras, monitors, and printers) to maintain accurate color consistency of an image from the point of capture through the output stage.
A printing method in which the printer sprays micro-jets of ionized ink at a sheet of paper in droplet sizes as small as 2 picoliters. Magnetized plates in the ink’s path direct the ink onto the paper in the desired shapes and patterns to make an image.
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. Although traditional cameras don’t have a specific ISO rating, digital cameras do as a way to calibrate their sensitivity to light. ISO is equivalent to the older ASA. More Info.
JPEG (Joint Photographic Experts Group)
The de facto standard for image compression in digital imaging devices. JPEG is a “lossy” compression format, capable of reducing a digital image file to about 5% of its normal size. The resulting decompression of the file can cause “blockiness,” “jaggies,” or “pixelization” in certain digital images. The greater the compression levels, the more of a chance pixelization or “blockiness” will occur. The greater the pixel count, the less of a chance pixelization will occur.
1,024 bytes, written kB, is used to refer to the size of an image file. This relates to the amount of information or image data, the file contains.
LCD (Liquid Crystal Display)
LCD screens, usually found on the rear of digital cameras, allow you to preview and review photographs you are about to take or have taken.
A type of rechargeable battery that was originally developed for use with camcorders and is now used as a power source for most digital still cameras and camcorders.
A data compression technique that can reduce the detail of a digital image file. Most video compression techniques utilize lossy compression.
1,024 Kilobytes, written MB, is used to refer to the size of files or media, such as hard drives. The number refers to the amount of information or image data in a file or how much information can be contained on a memory card, CD or DVD, hard drive or disk.
A megapixel contains 1,000,000 pixels and is the unit of measure used to describe the size of the sensor in a digital camera.
The camera’s file-storage medium. Most cameras use flash memory, which is a safe, highly reliable form of storage that doesn’t need the power to hold the images after they are saved. Flash memory won’t erase the images unless the user chooses to do so.
NiCad (Nickel Cadmium ) Battery
A type of rechargeable battery, the NiCad battery was one of the first successful rechargeable batteries used in small electronics, such as digital cameras.
NiMH ( Nickel-Metal Hydride) Battery
A commonly used rechargeable battery for digital cameras and camcorders. A NiMH battery can offer two to three times the capacity of an equivalent size NiCad battery.
A common pain in digital photography, noise is the appearance of color artifacts in a digital image. Mostly noticeable in the shadow areas of images captured at higher ISO ratings, the image processors used in many current digital cameras utilize noise-suppression software to minimize the appearance of noise artifacts.
A process in a digital camera’s image processor in which the artifacts caused by “pushed” ISO ratings or other electrical or heat-related artifacts are suppressed or eliminated in an image.
Non-lossy (aka lossless)
A term that refers to data compression techniques that do not remove image data details, to achieve compression. This method is generally less effective than lossy methods in terms of reducing file size since the entire original image is retained.
A type of memory card that retains data when power is turned off. Camera memory cards (CompactFlash, SD, SmartMedia, etc.) use non-volatile memory.
Another name for a zoom lens, which is a lens that enables the user to change the magnification ratio, i.e., the focal length of the lens, either by pushing, pulling or rotating the lens barrel. Unlike variable focal length lenses, zooms are constructed to allow a continuously variable focal length, without disturbing focus.
The result of recording too much light when taking a picture, which results in a lighter image. In digital imaging, overexposure can usually be corrected to a certain extent by the use of image-editing software, depending on the degree to which an image is overexposed. Raw files offer more latitude than JPEGs and TIFFs for correcting overexposure. More Info.
The difference between the image, as seen by a camera’s viewing system, and the image recorded by the imaging sensor. In point-and-shoot cameras, this variance increases as subjects move closer to the lens. Only through-the-lens (TTL) viewing systems are adjusted to avoid parallax error.
The breakup of a digital image file that has been scaled up (enlarged) to a point where the pixels no longer blend together to form a smooth image.
PNG (Portable Network Graphics)
Developed as a patent-free alternative to GIF, this format is used for lossless compression for purposes of displaying images on the World Wide Web.
Many pro and semi-pro digital cameras include the option for capturing raw files, which—unlike JPEGs, TIFFs, and other file formats—contain all of the data captured during the exposure in an unedited format. When processed, raw files can be adjusted far more extensively than images captured in other imaging formats.
Red-eye is the term used to describe the reddened pupils of a subject’s eyes that sometimes occurs when photographing people or pets with an electronic flash.
A method of reducing or eliminating red-eye from flash photographs by using a short burst of light, or pre-flash, to momentarily “stop-down” the pupils of the subject’s eyes prior to the actual flash exposure.
The ability to trip the camera shutter from a distance using a cable release or wireless transmitter/transceiver.
Refers to the number of pixels, both horizontally and vertically, used to either capture or display an image. The higher the resolution, the finer the image detail will be.
RGB Color (Red Green Blue)
RGB is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors for representation and display as images on computers and other digital devices.
Saturation is the depth of the colors within a photographic image. Photographs with deep levels of color are described as being heavily saturated. A photograph with lighter levels of saturation is described as having a muted color palette. A totally desaturated color photograph becomes monotone—or black and white.
SD Card (Secure Digital)
Far smaller than CompactFlash (CF) cards, Secure Digital memory cards have enabled camera manufacturers to further reduce the size of digital cameras.
A mechanism in the camera that controls the duration of light transmitted to the film or sensor. More Info.
A metering mode in which the shutter speed is fixed and the exposure is controlled by opening or closing the lens aperture.
The length of time the shutter remains open when the shutter release is activated, most commonly expressed in fractions or multiples of a second. More Info.
Spot metering is the measurement of light of a very small portion of the total image area.
A series of photographs captured over a period of time. These images can be captured in variable or set time intervals over the course of seconds, minutes, hours, days, weeks, etc.
TTL (Through the Lens)
TTL refers to a metering system that determines the proper exposure based on measuring the light that strikes the imaging sensor (or film plane) after passing through the camera’s lens.
The result of recording too little light when taking a picture, which results in a dark image. More Info.
I hope this has been useful, if you have suggestions, feel free to comment and I will add them.