Lenses, Focus & Exposure

An anamorphic lens squeezes a wide field of view horizontally onto film or a sensor, and the image is unsqueezed into widescreen later; its optical side effects — horizontal streak flares, oval bokeh and gently bending edges — became a signature of the big-screen look.

Deep focus keeps foreground, middle ground and background sharp at the same time, so the director can stage action on several planes at once and let the viewer choose where to look.

Depth of field is the zone in front of and behind the point of focus that looks acceptably sharp; aperture, focal length, focus distance and format size decide whether it is razor-thin or stretches to the horizon.

A fisheye lens is an extreme wide-angle lens (often around 180°) that abandons straight-line perspective and bends lines into curves, producing a bulging, distorted image that feels claustrophobic, comic or hallucinatory.

Focal length, measured in millimetres, sets a lens's angle of view: short focal lengths see wide and stretch space, long ones see narrow and compress it — which is why the same framing feels different on 24mm and on 135mm.

A rack focus shifts focus during a shot from one subject to another at a different distance, moving the viewer's attention — and often revealing new information — without a cut.

Shallow depth of field keeps only a thin slice of the scene sharp — often just the eyes — while everything nearer and farther dissolves into blur, isolating the subject and steering attention.

A telephoto (long) lens has a narrow angle of view that magnifies distant subjects; used from far away it compresses space, stacking the background onto the subject — the look of long-lens crowd shots, heat-haze chases and isolated faces.

A wide-angle lens has a shorter focal length than normal: it takes in more space, exaggerates the distance between near and far, and enlarges whatever is close to the camera — from immersive interiors to unsettling, distorted close-ups.

A split diopter is a half-lens attachment that lets one side of the frame focus close and the other far away, so a face in the foreground and a figure in the background are both sharp — with a tell-tale soft seam between them.

Aperture is the adjustable opening inside a lens that controls how much light reaches the film or sensor; opening it up brightens the image and makes depth of field shallower, stopping down does the opposite.

Bokeh is the character of the out-of-focus areas of an image — above all how point lights melt into soft discs or ovals — shaped by the lens design, the aperture blades and how shallow the focus is.

Dynamic range is the span between the darkest shadow and the brightest highlight a camera or film stock can record with detail, measured in stops; the wider it is, the less you lose to crushed blacks or blown-out windows.

The exposure triangle is the balance of aperture, shutter speed and ISO: change one and you must compensate with another, and each choice also changes depth of field, motion blur or noise.

Shutter speed is how long each frame is exposed to light; on cine cameras it is often set as a shutter angle, and it controls both brightness and how much blur movement leaves.

A tilt-shift lens can tilt its plane of focus relative to the sensor; tilted to leave only a thin, angled band sharp across a high-angle view of a city or landscape, it makes real places look like toy models.

A lens filter is glass placed in front of (or behind) the lens to change the image in camera: ND filters cut light, polarizers remove reflections, diffusion and mist filters soften detail and bloom highlights, color filters shift the tone.

Focus is where the lens places its plane of sharpness; on set it is set and adjusted during the take by the focus puller (1st AC), and deciding what is sharp is one of the strongest ways to direct the viewer's attention.

Lens distortion is the way a lens bends lines that should be straight — outward like a barrel on wide and fisheye lenses, inward like a pincushion on some long lenses; filmmakers either correct it or push it to make a space feel warped and unstable.

A long exposure keeps the shutter open for a long time, so still things stay crisp while anything moving — car lights, water, crowds, stars — smears into streaks and silky blur.

A macro shot uses a macro lens, extension tubes or diopters to focus extremely close and fill the frame with tiny details — the iris of an eye, a match head catching fire, an insect — at life size or larger.

Motion blur is the smear a moving subject leaves when it travels during the exposure of a frame; its amount depends on shutter speed or shutter angle, and it makes movement feel smooth, fast or, when exaggerated, frantic.

A normal lens has a field of view and perspective that feel close to natural vision for its format — roughly 40–50mm on 35mm film or full frame — so space looks neither stretched nor compressed.

Overexposure happens when too much light reaches the film or sensor: highlights clip to pure white and lose detail; used on purpose it reads as heat, memory, the afterlife or a dreamlike glare.

Soft focus is a deliberately dreamy image in which the subject is still in focus but fine detail and contrast are softened and highlights bloom — produced by special lenses, diffusion filters or even a stocking over the lens, a classic of Hollywood glamour close-ups.

Underexposure is when too little light reaches the film or sensor: shadows sink into black and noise rises; controlled, it hides information and builds dread in night, thriller and horror scenes.