APERTURE - The size of the opening in the lens. Think of the lens as a window—large windows let in more light, while small windows let in less light. A wide open aperture will let more light into the image for a brighter photo, while a smaller aperture lets in less light.
- 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.
- 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.
- How light or dark an image is. An image is created when the camera sensor (or film strip) is exposed to light—that’s where the term originates. A dark photo is considered underexposed, or it wasn’t exposed to enough light; a light photo is overexposed or exposed to too much light. Exposure is controlled through aperture, shutter speed and ISO.
F-STOP - 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.
INCIDENT & REFLECTIVE LIGHT METERING - Incident light is the light that falls on a subject, whether it comes from a direct or indirect source. Reflected light is a light source that initiates from the presence of incident light. In other words, it’s the light that bounces, or reflects, off the presence of reflective materials in your scene.
ISO - 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.
LENS FLARE - Created when non-image forming light enters the lens and subsequently hits the camera's film or digital sensor. This often appears as a characteristic polygonal shape, with sides which depend on the shape of the lens diaphragm. It can lower the overall contrast of a photograph significantly and is often an undesired artifact, however some types of flare may actually enhance the artistic meaning of a photo.
MACRO LENS - Lens that focuses very close to the subject allowing for 1:1 reproduction size of the object or larger.
MEDIUM FORMAT - Film and digital cameras that record images on media larger than 24 by 36 mm (used in 35 mm photography), but smaller than 4 by 5 inches (which is considered to be large-format photography).
RULE OF THIRDS - This compositional rule suggests imagining the image has been divided into three parts both horizontally and vertically. Often the most interesting compositions result in placing the subject on one of the intersections of those imaginary lines, instead of in the center of the photo.
SHUTTER SPEED - The amount of time the shutter is opened during an exposure. The shutter speed controls motion. Use a fast speed (like 1/2000th of a second) to freeze motion, or a slow one (1/4 of a second or longer) to blur moving objects.
VIEWFINDER - System used for composing and focusing on the subject being photographed. Aside from the more traditional rangefinder and reflex viewfinders, many compact digital cameras utilize LCD screens in place of a conventional viewfinder as a method of reducing the camera’s size (and number of parts).
WIDE ANGLE LENS - A lens that shows a wider field of view than a normal lens, which allows more to be fit into the frame. Depending on the degree of wide angle there may also be edge distortion (super wide angle), and if you get wide enough the image will become a circle (fish-eye).
35mm (135) FILM - The most common photographic film format. The film is 35mm wide, and each standard image is 24×36mm. Individual rolls of 35mm film are enclosed in single-spooled light-tight metal canisters. This allows cameras to be loaded even in broad daylight. The end of the film is cut on one side to form a leader so that it is easy for the film to be inserted into a corresponding slot in the camera’s take-up spool. 135 format film comes in both positive and negative, black and white, color, and infrared.
120 FILM - Roll film which is nominally 60 mm wide. The length of film is typically 30 inches (760 mm) up to 32–33 inches (810–840 mm), attached to a piece of backing paper longer and slightly wider than the film. The backing paper protects the film while it is wound on the spool, with enough extra length to allow loading and unloading the roll in daylight without exposing any of the film. Frame number markings for three standard image formats (6×4.5, 6×6, and 6×9; see below) are printed on the backing paper.