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Sensors & Digital Capture

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Sensors & Digital Capture

Hot Pixel

A photosite with abnormally high dark current that records as a bright coloured dot in long exposures.

count
Sensors & Digital Capture

Image Sensor

The silicon chip that converts light into an electrical signal, forming the digital equivalent of film.

mm
Sensors & Digital Capture

Infrared Cut Filter

A filter bonded in front of the sensor that blocks infrared and ultraviolet light to which silicon is sensitive but the eye is not.

nm
Sensors & Digital Capture

ISO Invariance

The property of a sensor whose noise is essentially the same whether a file is brightened by raising ISO in camera or by lifting exposure…

Sensors & Digital Capture

Line Skipping

Reading only a fraction of a sensor's rows to produce a lower-resolution image quickly, discarding the rest.

Sensors & Digital Capture

Linear Response

The property of a digital sensor that its output is directly proportional to the number of photons received.

Signal ∝ photons
Sensors & Digital Capture

Long Exposure Noise Reduction

A camera function that records a second, unexposed frame of equal duration and subtracts its noise pattern from the image.

Sensors & Digital Capture

Megapixel

One million pixels, the standard unit for stating a sensor's resolution.

MP = width × height / 1,000,000 MP
Sensors & Digital Capture

Microlens Array

A layer of tiny lenses, one above each photosite, that gathers light which would otherwise fall on the gaps between them.

Sensors & Digital Capture

Moiré

A false pattern of wavy bands or colour that appears when fine repeating detail in a subject interferes with the sensor's pixel grid.

Sensors & Digital Capture

Noise Floor

The level of background noise below which no real signal can be distinguished.

e⁻ (electrons)
Sensors & Digital Capture

Nyquist Limit

The highest spatial frequency a sensor can record correctly, equal to half its sampling rate.

f_Nyquist = 1 / (2 × pixel pitch) lp/mm
Sensors & Digital Capture

Optical Low-pass Filter

A birefringent layer in front of the sensor that slightly blurs the image to prevent detail finer than the pixel grid from being recorded.

Sensors & Digital Capture

Phase-detect Pixel

A photosite masked on one side, or split in two, so it sees the scene through only part of the lens and can contribute to focus measurement.

count
Sensors & Digital Capture

Photodiode

The semiconductor junction within a photosite that converts arriving photons into electrical charge.

e⁻ (electrons)
Sensors & Digital Capture

Photosite

A single light-collecting element on a sensor, corresponding to one pixel in the final image.

µm
Sensors & Digital Capture

Pixel Binning

Combining the signal from several adjacent photosites into one output pixel to improve signal-to-noise ratio.

SNR gain ≈ √n × (2×2, 4×4)
Sensors & Digital Capture

Pixel Pitch

The centre-to-centre distance between adjacent photosites on a sensor.

Pitch = sensor width / horizontal pixels µm
Sensors & Digital Capture

Pixel Shift Multi-shot

A mode that moves the sensor by precise sub-pixel amounts between exposures and combines the frames into one higher-quality image.

count (4, 8, 16 frames)
Sensors & Digital Capture

Quantum Efficiency

The proportion of photons striking a photosite that are actually converted into measurable signal.

QE = electrons / photons %
Sensors & Digital Capture

Raw Bit Depth

The number of bits used to record each photosite's value in a raw file, determining how many tonal levels are captured.

Levels = 2^bits bits
Sensors & Digital Capture

Raw Data

The minimally processed values read from the sensor, before demosaicing, white balance or tone rendering.

ADU
Sensors & Digital Capture

Read Noise

Noise introduced by the process of reading and digitising the sensor's signal, independent of how much light was captured.

e⁻ (electrons)
Sensors & Digital Capture

Readout Speed

How quickly a sensor's entire array can be transferred off the chip, usually quoted as the time to scan the full frame.

ms