Image sensor and film stock Cinematography can begin with rolls of film or a digital image sensor. Advancements in film emulsion and grain structure provided a wide range of available film stocks. The selection of a film stock was one of the first decisions made in preparing a typical 20th century film production. Aside from the film gauge selection Ч 8 mm (amateur), 16 mm (semi-professional), 35 mm (professional) and 65 mm (epic photography, rarely used except in special event venues) Ч the cinematographer has a selection of stocks in reversal (which, when developed, create a positive image) and negative formats along with a wide range of film speeds (varying sensitivity to light) from ISO 50 (slow, least sensitive to light) to 800 (very fast, extremely sensitive to light) and differing response to color (low saturation, high saturation) and contrast (varying levels between pure black (no exposure) and pure white (complete overexposure). Advancements and adjustments to nearly all gauges of film created the "super" formats wherein the area of the film used to capture a single frame of an image is expanded, although the physical gauge of the film remains the same. Super 8 mm, Super 16 mm and Super 35 mm all utilize more of the overall film area for the image than their "regular" non-super counterparts. The larger the film gauge, the higher the overall image resolution clarity and technical quality. The techniques used by the film laboratory to process the film stock can also offer a considerable variance in the image produced. By controlling the temperature and varying the duration in which the film is soaked in the development chemicals and by skipping certain chemical processes (or partially skipping all of them), cinematographers can achieve very different looks from a single film stock in the laboratory. Some techniques that can be used are push processing, bleach bypass and cross processing. Although the majority of cine a still uses film, much of modern cinema uses digital cinematography and has no film stocks, but the cameras themselves can be adjusted in ways that go far beyond the abilities of one particular film stock. They can provide varying degrees of color sensitivity, image contrast, light sensitivity and so on. One camera can achieve all the various looks of different emulsions, although it is heavily argued as to which method of capturing an image is the "best" method. Digital image adjustments (ISO, contrast etc.) are executed by estimating the same adjustments that would take place if actual film were in use, and are thus vulnerable to the cameras sensor designers perceptions of various film stocks and image adjustment parameters. Filters Filters, such as diffusion filters or color-effect filters, are also widely used to enhance mood or dramatic effects. Most photographic filters are made up of two pieces of optical glass glued together with some form of image or light manipulation material between the glass. In the case of color filters, there is often a translucent color medium pressed between two planes of optical glass. Color filters work by blocking out certain color wavelengths of light from reaching the film. With color film, this works very intuitively wherein a blue filter will cut down on the passage of red, orange and yellow light and create a blue tint on the film. In black-and-white photography, color filters are used somewhat counter intuitively; for instance a yellow filter, which cuts down on blue wavelengths of light, can be used to darken a daylight sky (by eliminating blue light from hitting the film, thus greatly underexposing the mostly blue sky), while not biasing most human flesh tone. Certain cinematographers, such as Christopher Doyle, are well known for their innovative use of filters. Filters can be used in front of the lens or, in some cases, behind the lens for different effects.