Exposure
How much light reaches the sensor while you take the picture.
Stop
A step that doubles or halves the light.
Aperture
also called the lens opening
The opening in the lens, which you can make wider or narrower. A wider aperture lets in more light and makes the sharp zone thinner.
f-number
The size of the aperture, written like f/2.8. It runs back to front: a small number (f/1.4) is a wide aperture, a big number (f/16) a narrow one.
Shutter speed
also called exposure time
How long the shutter stays open. A slower shutter speed lets in more light, and anything moving blurs more.
ISO
also called brightening
How much the camera brightens the picture after the light's come in. It doesn't add any light.
Noise
also called grain
Speckles, worst in the dark areas. They mostly come from too little light.
Sharp zone
also called depth of field
The stretch from the nearest sharp thing to the furthest. Sharpness fades gradually rather than stopping at a line.
Focus distance
How far away the camera's focused. The sharp zone sits around it.
Focal length
How zoomed-in the lens is, in millimetres.
Angle of view
How wide a slice of the world fits in the frame.
Perspective
How big near things look next to far ones. Only moving closer or further away changes it.
Motion blur
The smear left when something moves while the shutter's open.
Meter
The camera's light gauge. Zero means about right.
Program (P)
The camera picks the aperture and the shutter speed. Switch to A or S to choose one of them yourself.
Aperture priority (A/Av)
You pick the aperture and the camera picks the shutter speed.
Shutter priority (S/Tv)
You pick the shutter speed and the camera picks the aperture.
Manual (M)
You pick everything. The meter tells you if it's too dark or too bright.
Auto ISO
The camera changes ISO to keep the picture about right.
Circle of confusion
The biggest blur spot that still looks sharp.
Hyperfocal distance
Focus here and everything from half this distance to the horizon is sharp.
Diffraction
Light spreading out as it squeezes through a very narrow aperture, which softens fine detail. It's why the narrowest aperture isn't the sharpest.
Camera shake
Blur from your hands moving the camera. It smears the whole picture, not just what's moving.
Stabiliser
Steadies the camera against your hands, so you can hand-hold slower shutter speeds. It can't freeze something that's moving.
Minimum focus distance
The closest the lens can focus. The focus ring stops there.
EV100
One number for how bright a scene is, or how much light your settings let in.
Blinking value
A number the camera can't set far enough. The picture stays off until you change another dial.
Light ledger
The two bars under the picture: light in (the aperture and the shutter speed) and ISO's brightening.
Idealised lens
A make-believe lens that opens to f/1.4 at any focal length.
