Bokeh: A term referring to the aesthetic quality of an image’s out of focus area.

Depth of Field: The amount of the image that is in focus. A shallow depth of field has only a small area in focus with the rest blurred. Controlled by the size of the aperture.

Dot: A single point of light displaying only Red, Green, or Blue.

Dynamic Range: Describes the range between the darkest values in an image and the brightest ones. Cameras typically have a much narrower dynamic range than the human eye.

Image Stabilization: A means of correcting for hand-shake in slower exposures, allowing crisper shots in fading light. Does not correct for movement of subjects, just the jitter caused by the photographer’s hands. Comes in three basic flavors:

• Sensor-Shift: Also called “In-Body,” the actual sensor is mounted on a gyroscopic device that keeps the sensor steady even while the camera shakes. Offers the advantage of adding IS to any lens mounted to the camera. Used by Olympus, Sony, and Pentax.
• Lens-Shift: Elements with the lens shift to project a stable image onto the sensor. Offers the advantage of seeing the IS in action through the viewfinder, but has to be added per lens. Used by Canon, Nikon, and Panasonic.
• Digital Image Stabilization: Not a true form of IS (similar to “digital zoom”), this is a marketing term used when a camera will automatically select a higher ISO to obtain faster shutter speeds. The disadvantage to this system is that it increases noise, sometimes very rapidly, as it raises the ISO.

JPEG (JPG): Joint Photo Experts Group. A standard image format which uses compression to reduce file size.

Lossless: A form of compression where no data is discarded.

Lossy: Refers to a form of compression where some information is permanently discarded to save space.

OOF: Out of Focus.

Pixel: Short for “Picture Element”. A standard unit of imaging representing one point of combined light. Usually comprised of three “dots.”

RAW: An image format that has not been processed or compressed, as close to the actual information recorded by the sensor as possible.

TIFF: Tagged Image File Format, a format that supports lossy and lossless compressions. Creates larger files than JPEG.

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AD: Anomalous Dispersion

AF: Auto Focus

AF-S: Auto Focus Silent. Nikon lens type using Silent Wave Motor.

APO: Apochromatic, designates Sigma lenses which use exotic lens correction elements to correct aberrations.

ASL: Aspherical Lens Element, Tamron designation

ASP: Aspherical Lens Element, Sigma designation

Aperture: The diameter of the opening allowing light through the lens, usually controlled by a variable diaphragm. The wider the aperture the more light that is let through and the narrower the depth of field. Going to a larger aperture is often referred to as “opening” or “stopping up” the aperture. Going to a smaller aperture is often referred to as “closing” or “stopping down” the aperture.

CONV.: Sigma designation stating teleconvertor compatability.

D: Designation on some older Nion lenses that indicated the presence of a distance encoder chip. Has since become standard.

DC:

• Nikon: Defocus Control. Nikon feature offering a separate control ring to control spherical aberration, affecting the bokeh of an image.
• Sigma: Digital Crop, Sigma lenses designed for digital SLR cameras. (Not “Full Frame”)

DG: Designed for Digital, Sigma lenses designed to have better optical corrections than older lenses for use with both film and digital bodies (“Full Frame”)

DI: Digitally Integrated Design. Tamron designation for lenses suitable for both film and digital usage. (“Full Frame”)

Di-II: Digitally Integrated Design. Tamron designation for lenses intended for DSLRs only. (Not “Full Frame”)

DOF: Depth of Field

DX: For use with Nikon cameras with DX sized sensors. (Not “Full Frame”)

ED: Extra-low Dispersion Glass

EF: “Electro-Focus” Standard lens mount for Canon EOS cameras. (“Full Frame”)

EF-S: “Electro-Focus Short Back Focus” Lens mount for digital Canon EOS cameras with APS-C sized sensors. (Not “Full Frame”)

ELD: Extraordinary Low Dispersion Glass Element

EX: A premium paint used by Sigma to denote its top-end lenses.

F (f): Designates the aperture value of a lens. The smaller the F number, the larger the aperture. Lenses are usually listed by their maximum (widest) F value(s).

Focal Length: The functioning distance between the lens elements and the sensor. Shorter focal lengths are considered to be ‘wide’ while larger ones are considered ‘telephoto.’ Affects and determines how much of a scene the camera will “see.”

G:

• Nikon: Indicates the absence of a physical aperture ring
• Sony: Deotes Sony's top-range Sony-branded lenses.

HSM: Hyper-Sonic Motor. Sigma’s fastest focusing system.

IF: Inner (or Internal) Focus. The front element of the lenses stays put and does not extend or rotate during focusing.

IS: Image Stabilization

LD: Low Dispersion Glass Element

MFD: Minimum Focusing Distance

Macro: Lens recreates image on the sensor at a ratio of 1:4 with a goal of 1:1, meaning the image produced is done so at or close to actual size. If a subject in real life is 1cm long, a 1:1 ratio would display it 1cm long on the sensor. How much of the frame is filled depends on the size of the sensor beyond this point.

Mega O.I.S.: Mega Optical Image Stabilization. Panasonic’s branding for lens-shift IS.

Minimum Focusing Distance: The shortest distance between the lens and the subject which will result in a sharply focused image.

Mount: The particular method used for attaching the lens to the camera body. Varies from manufacturer to manufacturer.

Nikkor: Brand-name for Nikon lenses.

OS: Optical Stabilization. Sigma’s branding for lens-shift IS.

Prime: A lens with a single focal length, such as 50mm or 25mm. They were the most common type of lens in the film days and used to be faster and sharper than zoom lenses.

RF: Rear Focus

SLD: Special Low Dispersion Glass Element

SWD: Sonic Wave Drive. Olympus' fastest focusing system.

Telephoto: Typically refers to lenses with a longer than average focal length. Telephoto lenses have narrower fields of view which makes them appear to ‘zoom’ in on subjects.

USM: Ultra-Sonic Motor. Denotes Canon’s fastest focusing system.

VC: Vibration Compensation. Tamron’s branding for lens-shift image stabilization.

VR: Vibration Reduction. Nikon’s branding for lens-shift image stabilization.

Wide Angle: These lenses have a wider field of view than the human eye (approximately 45 degrees), allowing more of a scene to be recorded in a frame.

XR: Extra Refractive Index Glass

Zoom: These lenses cover a range of focal lengths to provide versatility. They usually compromise by having slower maximum apertures than primes, or else are usually expensive pro-grade lenses.

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4/3 (Four Thirds): A system proposed by Olympus that uses sensors designed for a 4:3 aspect ratio (like that used for computer screens and older televisions) instead of the traditional 3:2 aspect ratio of 35mm film and APS-C sensors. (2x Crop Factor)

AE: Auto Exposure

AEL: Auto Exposure Lock

AFL: Auto Focus Lock

APS-C: Advanced Photo Systems type-C. Sensor format with a 3:2 aspect ratio, which is smaller than a 35mm negative and is therefore not considered to be ‘full-frame.’ Lenses designed for full-frame sensors will produce an image that appears to be ‘cropped’ or to have a further zoom effect than it would have on a full-frame sensor.

Buffer: An amount of internal memory used to store photos as they’re being written to a memory card.

CCD: Charge-Coupled Device. A common type of imaging sensor.

CMOS: Complimentary Metal-Oxide Semiconductor. A common type of imaging sensor.

Crop Factor: Used to talk about sensors smaller than a 35mm film imaging area. Represented as the number of times the sensor area would go into the 35mm area. (ie, 1.5x, 1.6x, 2x)

Diopter: A unit of measure for the optical power of a lens. Some cameras allow the diopter of their viewfinder to be adjusted to be in focus at different distances from the eye.

DSLR: Digital Single-Lens Reflex. These cameras use a movable mirror above the image sensor to reflect light through some form of optical viewfinder. The mirror is then raised to allow the light to hit the image sensor. DSLRs also use interchangeable lenses.

DX: A Nikon designation for their APS-C sized sensor. (1.5 Crop Factor)

EOS: Electro-Optical System. Canon’s designation for its SLR and DSLR systems.

EVF: Electronic Viewfinder. These cameras use a small LCD instead of a mirror and optic system for their viewfinder.

FPS: Frames Per Second. The rate at which a camera is capable of taking pictures.

Full-Frame: The image sensor is the same size as a 35mm film’s imaging area.

FX: A Nikon designation for a full-frame sensor.

ISO: International Standards Organization. The rate at which both film and digital sensors can absorb light. The larger the number, the faster the light absorption and the shorter the exposure time, however the larger the number the more degradation (‘grain’ in film, ‘noise’ in digital) the image exhibits. ISO settings are referred to as ‘speeds.’ ie. ‘400 speed’

K: Degrees Kelvin, used to measure the color temperature of light. Redder and yellower lights have lower Kelvin temperatures, bluer lights have higher Kelvin temperatures.

LCD: Liquid Crystal Display.

LiveMOS: A type of imaging sensor used in DSLRs which can output the image directly through to the LCD screen, much like on point-and-shoot cameras.

LiveView: A system where the image hitting the sensor is displayed live on the rear LCD. Common in point-and-shoots, less standard on DSLRs.

Megapixel: Designates the size of image a sensor is capable of capturing, determined by multiplying the maximum image height by the maximum image width (in pixels)

MP: Megapixel.

OIS: Optical Image Stabilization.

Point and Shoot: A common name for compact cameras designed for ease-of-use. Frequently refers to digital compact cameras which rely heavily on a rear LCD as a viewfinder and which usually rely mostly an automated settings. Point and Shoots do not have interchangeable lenses like DSLRs do, although some models have available lens convertors.

TFT: Thin Film Transistor. A common way of making LCD screens which results in a more stable (and easy to see) image.

TTL: Through the Lens. Uses exposure information based on light coming into the lens.

Ultra Zoom: An informal designation for Point and Shoot cameras with atypically large optical zoom ranges, typically 12x or larger.

WB: Whie Balance

White Balance: Used to correct the temperature of light hitting the sensor in order to reproduce color more accurately.

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CF: Compact Flash

MMC: MultiMedia Card

Memory Stick: Memory format used mostly by Sony.

UDMA: Ultra Direct Memory Access, a protocol which allows flash memory cards to transfer data even faster.

SD: Secure Digital

SDHC: Secure Digital High Capacity. Similar to SD but supports capacities greater than 2 gigabytes.

xD: Extreme Digital, used mostly by Olympus.

X Speed: x = 150 kilobytes per second. Denotes the speed at which a card can read or write data. If not specified, the speed typically refers to the maximum sustained write speed. (ie, 133x, 300x)

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AW: All Weather Cover

M.A.S: Modular Accessory System

S.A.S: Sleeve Accessory System

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