Sensors & Digital Capture — 60 Terms Defined

Hot Pixel Sensors & Digital Capture count A photosite with abnormally high dark current that records as a bright coloured dot in long exposures.

Image Sensor Sensors & Digital Capture mm The silicon chip that converts light into an electrical signal, forming the digital equivalent of film.

Infrared Cut Filter Sensors & Digital Capture nm A filter bonded in front of the sensor that blocks infrared and ultraviolet light to which silicon is sensitive but the eye is not.

ISO Invariance Sensors & Digital Capture 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 in processing.

Line Skipping Sensors & Digital Capture Reading only a fraction of a sensor's rows to produce a lower-resolution image quickly, discarding the rest.

Linear Response Sensors & Digital Capture The property of a digital sensor that its output is directly proportional to the number of photons received. Signal ∝ photons

Long Exposure Noise Reduction Sensors & Digital Capture A camera function that records a second, unexposed frame of equal duration and subtracts its noise pattern from the image.

Megapixel Sensors & Digital Capture MP One million pixels, the standard unit for stating a sensor's resolution. MP = width × height / 1,000,000

Microlens Array Sensors & Digital Capture A layer of tiny lenses, one above each photosite, that gathers light which would otherwise fall on the gaps between them.

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

Noise Floor Sensors & Digital Capture e⁻ (electrons) The level of background noise below which no real signal can be distinguished.

Nyquist Limit Sensors & Digital Capture lp/mm The highest spatial frequency a sensor can record correctly, equal to half its sampling rate. f_Nyquist = 1 / (2 × pixel pitch)

Optical Low-pass Filter Sensors & Digital Capture A birefringent layer in front of the sensor that slightly blurs the image to prevent detail finer than the pixel grid from being recorded.

Phase-detect Pixel Sensors & Digital Capture count 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.

Photodiode Sensors & Digital Capture e⁻ (electrons) The semiconductor junction within a photosite that converts arriving photons into electrical charge.

Photosite Sensors & Digital Capture µm A single light-collecting element on a sensor, corresponding to one pixel in the final image.

Pixel Binning Sensors & Digital Capture × (2×2, 4×4) Combining the signal from several adjacent photosites into one output pixel to improve signal-to-noise ratio. SNR gain ≈ √n

Pixel Pitch Sensors & Digital Capture µm The centre-to-centre distance between adjacent photosites on a sensor. Pitch = sensor width / horizontal pixels

Pixel Shift Multi-shot Sensors & Digital Capture count (4, 8, 16 frames) A mode that moves the sensor by precise sub-pixel amounts between exposures and combines the frames into one higher-quality image.

Quantum Efficiency Sensors & Digital Capture % The proportion of photons striking a photosite that are actually converted into measurable signal. QE = electrons / photons

Raw Bit Depth Sensors & Digital Capture bits 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

Raw Data Sensors & Digital Capture ADU The minimally processed values read from the sensor, before demosaicing, white balance or tone rendering.

Read Noise Sensors & Digital Capture e⁻ (electrons) Noise introduced by the process of reading and digitising the sensor's signal, independent of how much light was captured.

Readout Speed Sensors & Digital Capture ms How quickly a sensor's entire array can be transferred off the chip, usually quoted as the time to scan the full frame.