Aperture
Exposure
The opening in a lens through which light passes, expressed as an f-stop (f/1.4, f/2.8, f/8). A wider aperture (lower f-number) lets in more light and produces shallower depth of field. A narrower aperture (higher f-number) lets in less light and increases depth of field.
Shutter Speed
Exposure
The duration the camera's shutter remains open, expressed in fractions of a second (1/500, 1/60) or whole seconds. Fast shutter speeds freeze motion. Slow speeds introduce motion blur and allow more light onto the film or sensor.
ISO / Film Speed
Exposure
A measure of a film's or sensor's sensitivity to light. Low ISO (50, 100) requires more light and produces finer grain or lower noise. High ISO (800, 3200) works in low light but introduces grain or digital noise. On film, ISO is fixed at time of purchase; digitally, it's adjustable per shot.
Exposure Value (EV)
Exposure
A single number that represents a combination of aperture and shutter speed producing the same exposure. EV 0 is defined as f/1 at 1 second. Each full stop of light equals one EV. Used to describe exposure compensation and light meter readings.
Metering
Exposure
The process of measuring scene brightness to determine correct exposure. Modes include evaluative/matrix (averaging the whole frame), center-weighted, spot (reads a small area), and highlight-weighted. Handheld incident meters measure the light falling on a subject rather than the light reflecting from it.
Exposure Bracketing
Exposure
Taking multiple frames of the same scene at different exposures (typically one stop under, correct, one stop over). Used to ensure a properly exposed frame in difficult lighting conditions, and on film where there's no immediate playback to verify the result.
Dynamic Range
Exposure
The range of brightness a medium can capture from the deepest shadows to the brightest highlights before detail is lost. Film typically has more forgiving highlight roll-off than digital sensors. Scenes with very high dynamic range (bright sun and deep shadow) often require compromise in exposure.
Zone System
Exposure
Developed by Ansel Adams and Fred Archer. Divides tonal range into 11 zones from pure black (Zone 0) to pure white (Zone X). Used to precisely pre-visualize how a scene will translate in the final print, and to plan exposure and development accordingly.
Reciprocity
Exposure
The principle that equivalent exposure is maintained by balancing aperture and shutter speed. Reciprocity failure occurs in film at very long exposures (typically beyond 1 second) where the film becomes less sensitive than expected, requiring additional exposure time beyond what the meter indicates.
Focal Length
Lens
The distance in millimeters between the lens's optical center and the film plane when focused at infinity. Shorter focal lengths (24mm, 35mm) produce wider fields of view. Longer focal lengths (85mm, 135mm) narrow the field of view and compress apparent depth. Standard for 35mm is approximately 43–50mm.
Depth of Field
Lens
The range of distance within a scene that appears acceptably sharp. Controlled primarily by aperture (wider = shallower), but also affected by focal length and subject distance. A wide aperture on a long focal length at close distance produces the shallowest depth of field.
Bokeh
Lens
The aesthetic quality of the out-of-focus areas in a photograph, derived from the Japanese word for blur. Determined by aperture blade shape, lens design, and rendering characteristics. Often described as smooth or swirly, harsh or busy. Not simply "blurriness" — it refers to the quality of how the blur appears.
Hyperfocal Distance
Lens
The closest focusing distance at which infinity is within the depth of field. When a lens is focused at hyperfocal distance, everything from half that distance to infinity appears acceptably sharp. Useful for zone focusing and street photography where speed matters more than precise focus.
Chromatic Aberration
Lens
A lens defect where different wavelengths of light focus at different points, creating color fringing around high-contrast edges. Longitudinal (axial) CA produces color fringing in front of and behind the focus plane. Lateral CA produces fringing at the edges of the frame. More common in faster and cheaper lenses.
Vignetting
Lens
Darkening of corners and edges of an image, most visible at wider apertures. Can be optical (a characteristic of the lens), mechanical (caused by a filter or hood blocking light), or pixel-level (in digital sensors). Often reduced by stopping down. Some photographers add it intentionally to draw focus to the center.
Lens Compression
Lens
The perceived flattening of depth between objects at different distances when using a longer focal length. Elements in the background appear larger and closer to the subject than they would with a wider lens from the same position. This is a function of shooting distance, not focal length alone.
Circle of Confusion
Lens
The size of the blur spot produced by a point of light that is not precisely in focus. When the circle of confusion is small enough to appear as a point to the eye (typically 0.03mm for 35mm), a point is considered "in focus." Depth of field calculations are based on a maximum acceptable circle of confusion.
Film Grain
Film
The random silver halide crystal structure visible in developed film, appearing as texture in the final image. Higher-speed films (ISO 400 and above) have larger grain. Fine-grain films (ISO 50, 100) resolve more detail but require more light. Grain is often considered aesthetically desirable in a way that digital noise is not.
Pushing Film
Film
Exposing film at a higher ISO than its box speed, then extending development time to compensate. Allows shooting in lower light. The tradeoff is increased grain, higher contrast, and reduced shadow detail. A common example: rating HP5 at ISO 1600 instead of 400 and pushing development by two stops.
Pulling Film
Film
Exposing film at a lower ISO than its box speed, then reducing development time. Used to reduce contrast in very bright conditions or with highly contrasty scenes. Results in finer grain and gentler tonal gradation. Less common than pushing.
Film Latitude
Film
How forgiving a film is to over or underexposure while still producing a usable image. Negative films (C-41, B&W) have wide latitude, especially in the overexposure direction. Slide/reversal films have very narrow latitude, often less than one stop in either direction, requiring precise exposure.
C-41 / E-6
Film
The two standard chemical processes for color film. C-41 produces color negatives (print film such as Kodak Gold, Portra, Fuji 400H). E-6 produces color reversal (slide or transparency film such as Fuji Velvia, Provia). Most labs in LA process C-41; E-6 is rare and increasingly specialty-only.
Contact Sheet
Film
A proof print made by placing a full strip of negatives directly onto photographic paper and exposing it. Each frame appears actual negative size. Used for editing and selecting frames before making full-size enlargements. A practical first step in the darkroom workflow.
Fixer
Film
A chemical solution used in film and darkroom processing to remove unexposed and undeveloped silver halides from the emulsion, making the image permanent and stable in light. Without fixing, a developed image would continue to darken when exposed to light. Sodium or ammonium thiosulfate are the most common agents.
Cross Processing (Xpro)
Film
Developing film in the wrong chemical process intentionally — most commonly, developing E-6 slide film in C-41 chemistry. Results in high contrast, saturated, shifted colors that are unpredictable and vary by film stock. Popular for fashion and editorial work in the 1990s and 2000s.
Rangefinder
Camera
A camera type with a viewfinder separate from the lens. Focus is achieved by aligning two superimposed images via a coupled rangefinder mechanism. Rangefinders are typically compact, quiet, and lack the mirror blackout of SLRs. Common examples: Leica M series, Voigtlander Bessa, Canonet.
SLR / DSLR
Camera
Single-Lens Reflex. A camera where you view through the actual taking lens via a mirror that flips up at the moment of exposure. Provides accurate framing and through-the-lens metering. The most common camera type for 35mm film photography from the 1960s onward and for digital until mirrorless became dominant.
Medium Format
Camera
Film cameras that use 120 or 220 roll film, producing frames larger than 35mm. Common frame sizes include 6x4.5cm, 6x6cm, 6x7cm, and 6x9cm. Larger negatives mean less enlargement is required, producing finer grain and greater tonal detail. Bodies include Hasselblad, Mamiya, Bronica, Pentax 67.
Zone Focusing
Camera
Pre-setting focus to a fixed distance and using a narrow enough aperture (f/8 or smaller) to ensure that subjects within an expected range are sharp, without requiring precise focus adjustment. Common in street photography for fast, quiet shooting. Most effective with wide to standard focal lengths.
Flash Sync Speed
Camera
The fastest shutter speed at which a camera can use a standard strobe flash without the shutter curtain partially obscuring the frame. Typically 1/125 to 1/250 second on focal plane shutter cameras. High-Speed Sync (HSS) allows flash at faster shutter speeds by pulsing the flash, though with reduced power.
Mirror Lock-Up
Camera
A feature on SLR cameras that allows the mirror to flip up before the shutter fires, reducing vibration caused by mirror slap. Important for sharp images at slower shutter speeds (roughly 1/15 to 1 second) when the camera is on a tripod. Particularly relevant for macro and telephoto shooting.
Light Meter
Camera
A device that measures light levels and calculates recommended exposure settings. Reflected light meters (built into cameras) measure light bouncing off a subject. Incident light meters measure light falling on a subject. Spot meters measure a very narrow angle of view for precise reading of specific tonal areas.
DX Coding
Camera
A system where 35mm film canisters are printed with a checkerboard pattern of electrically conductive silver and non-conductive squares that camera contacts read to automatically detect film ISO, exposure latitude, and number of exposures. Introduced in 1983. Cameras without DX reading require manual ISO setting.
Rule of Thirds
Composition
A compositional guideline that divides the frame into a 3x3 grid and places the subject or horizon along the grid lines or at their intersections. Generally produces more dynamic images than centering. A useful starting point, not a rule — compelling images regularly break it.
Leading Lines
Composition
Lines within the frame that draw the viewer's eye toward the subject or through the image. Can be roads, fences, shadows, architectural elements, or any linear feature. Diagonal leading lines create more energy than horizontal or vertical ones.
Negative Space
Composition
Empty or simple areas of a frame that surround the subject. Negative space gives the eye room to breathe, emphasizes the subject's shape, and can convey isolation, simplicity, or scale. Often underused by photographers who feel compelled to fill the frame.
Frame Within a Frame
Composition
Using elements within the scene (doorways, windows, arches, trees) to create a secondary frame around the primary subject. Adds depth and context, directs attention, and creates a sense of place. Particularly effective in architectural and environmental portraiture.
The Decisive Moment
Composition
Henri Cartier-Bresson's concept that the perfect photograph exists at a single moment where form, content, and geometry align simultaneously. The phrase captures both the physical timing of pressing the shutter and the cultivated visual awareness needed to recognize that moment before it passes.
Subject Isolation
Composition
Separating the primary subject from its background visually, achieved through shallow depth of field, tonal contrast, color contrast, or spatial positioning. A well-isolated subject is immediately clear to the viewer. Isolation can also be achieved through timing, waiting for a background to clear.
Visual Weight
Composition
The relative attention-drawing power of elements within the frame. Bright, high-contrast, large, or isolated elements carry more visual weight. A compositionally balanced frame distributes weight intentionally — either symmetrically or asymmetrically — to create a stable or dynamic feeling.
Foreground Interest
Composition
Including an element in the near foreground to create a sense of depth and draw the viewer into the frame. Particularly effective in landscape and environmental photography. A foreground element gives the eye an entry point before moving to the middle ground and background.