Methods of image capture

Since the first digital backs were introduced, there have been three main methods of capturing the image, each based on the hardware configuration of the sensor and color filters. The first method is often called single-shot, in reference to the number of times the camera's sensor is exposed to the light passing through the camera lens. Single-shot capture systems use either one CCD with a Bayer filter mosaic, or three separate image sensors (one each for the primary additive colors red, green, and blue) which are exposed to the same image via a beam splitter. The second method is referred to as multi-shot because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique. The most common originally was to use a single image sensor with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method is called Microscanning. This technique utilizes a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to "stitch" together a higher resolution image than the CCD would allow otherwise. A third version combined the two methods without a Bayer filter on the chip. The third method is called scanning because the sensor moves across the focal plane much like the sensor of a desktop scanner. Their linear or tri-linear sensors utilize only a single line of photosensors, or three lines for the three colors. In some cases, scanning is accomplished by moving the sensor e.g. when using color co-site sampling or rotate the whole camera; a digital rotating line camera offers images of very high total resolution. The choice of method for a given capture is determined largely by the subject matter. It is usually inappropriate to attempt to captu

e a subject that moves with anything but a single-shot system. However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scanning backs make them attractive for commercial photographers working with stationary subjects and large-format photographs. Dramatic improvements in single-shot cameras and raw image file processing at the beginning of the 21st century made single shot, CCD-based cameras almost completely dominant, even in high-end commercial photography. CMOS-based single shot cameras remained somewhat common.Primary colours are sets of colours that can be combined to make a useful range of colours. For human applications, three primary colours are usually used, since human colour vision is trichromatic. For additive combination of colours, as in overlapping projected lights or in CRT displays, the primary colours normally used are red, green, and blue. For subtractive combination of colours, as in mixing of pigments or dyes, such as in printing, the primaries normally used are cyan, magenta, and yellow,[1] though the set of red, yellow, blue is popular among artists.[2] See RGB colour model, CMYK colour model, and RYB colour model for more on these popular sets of primary colours. Any particular choice for a given set of primary colours is derived from the spectral sensitivity of each of the human cone photoreceptors; three colours that fall within each of the sensitivity ranges of each of the human cone cells are red, green, and blue.[3] Other sets of colours can be used, though not all will well approximate the full range of colour perception. For example, an early colour photographic process, autochrome, typically used orange, green, and violet primaries.[4] However, unless negative amounts of a colour are allowed the gamut will be restricted by the choice of primaries. The combination of any two primary colours creates a secondary colour.