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Binning is the procedure of combining a cluster of pixels from the camera sensor into a single pixel. As such, in 2x2 binning, an array of 4 pixels becomes a single larger pixel, reducing the overall number of pixels. This aggregation, although associated with loss of information, reduces the amount of data to be processed, facilitating the analysis. At the cost of a lower resolution, this procedure enhances the sensibility by reducing the impact of the read noise on the processed image and improves the signal to noise ratios and readout speeds.


A charge-coupled device (CCD) is an analogical or numerical electrostatic shifts-registering device. CCDs are made of a series of identical semiconductor elements (capacitive bins) that can store and transfer charges between bins. In response to an impulsion from the signal, all the bins transfer their charge to the adjacent bin at the same time. In a CCD image sensor, pixels are p-doped metal-oxide-semiconductors (MOS) capacitors. These capacitors allow the conversion of incoming photons into electron charges at the semiconductor-oxide interface; the CCD is then used to read out these charges. CCDs are very versatile and can be manipulated to achieve, e.g., a binning.

Impulse noise

Impulse Noise (IN) is a general term for single-pixel bright or dark spots that are not authentic imagery. This artifact can have several different causes, each with a slightly different appearance like bit-flip noise, transcription artifacts, fire noise, salt and pepper noise, low saturation noise, random noise, coherent noise.

Readout noise

The readout noise, also called preamplifier noise, is the main noise component that needs to be considered when ​choosing a camera. It is a combination of noise from the pixel and from the electronics that amplifies and digitizes the charge signal in the CCD readout. It basically determines the contrast resolution that the camera is able to achieve. The lower the readout noise level, the lower the minimum number of signal electrons that can be detected and higher the sensitivity of the sensor. A higher sensitivity allows for shorter exposure times which helps to limit dark noise and to see smaller changes in signal amplitude, thus detecting details with smaller contrast differences. Therefore, you need a sensor with a low readout noise to observe "dark scenes".

Shot noise

The shot noise is a quantum-limited intensity noise that originates from the discrete nature of electrons, hence its alternative name quantic noise. It is caused by the arrival process of light photons on the sensor. Consider the following example: imagine standing at an overpass above a highway and counting the amount cars passing by in one minute. The next minute, and the next, and the amount counted is probably not the same. The resulting measurement varies from minute to minute, following a Poisson distribution, hence its alternative name Poisson noise. In the electron domain this is similar: the standard deviation of the amount of captured electrons in a pixel is the square root of the mean signal level.

Thermal noise

The thermal noise, also called Johnson-Nyquist noise, is intimately linked to the dark current. It is caused by the natural movement of free electrons that increases with the sensor temperature. Cameras manufacturers quantify it by the amount of unwanted free electrons generated in the CCD due to thermal energy. On professional and research instruments, this noise can be efficiently reduced by cooling the sensor using the Peltier effect or ventilation in order to assure a constant temperature.

For mor information, see Dark current.

Dark Noise

Dark noise, also called dark current noise, is a statistical variation of the dark current and is the electron equivalent of photon shot noise. Dark current can be subtracted from an image, while dark noise remains. Dark noise is calculated from the dark current: Dark Noise = sqrt[(Dark current)(integration time)] Dark current noise is temperature and time-dependent – typically expressed in electrons per second at a given temperature. The shorter the exposure, the less dark current noise will be present in the image.


Dark-field microscopy (dark-ground microscopy) describes microscopy methods, in both light and electron microscopy, which exclude the unscattered beam from the image. As a result, the field around the specimen (i.e., where there is no specimen to scatter the beam) is generally dark. In optical microscopy, dark-field describes an illumination technique used to enhance the contrast in unstained samples. It works by illuminating the sample with light that will not be collected by the objective lens and thus will not form part of the image. This produces the classic appearance of a dark, almost black, background with bright objects on it.


Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. It is defined as the bending of light around the corners of an obstacle or aperture into the region of the geometrical shadow of the obstacle. In classical physics, the diffraction phenomenon is described as the interference of waves according to the Huygens–Fresnel principle.