It is important to note that one prism can serve many different purposes depending on orientation. For instance, take a 45° – 90° – 45° prism, commonly referred to as a right angle prism. If light enters at a right angle through one of the faces adjacent to the 45° angle (a leg face), there will be a single reflection and the incident ray will be deviated by 90°.

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For an interchangeable lens camera, the flange focal distance (FFD) (also known as the flange-to-film distance, flange focal depth, flange back distance (FBD), flange focal length (FFL), back focus[1] or register, depending on the usage and source) of a lens mount system is the distance from the mounting flange (the interlocking metal rings on the camera and the rear of the lens) to the film or image sensor plane. This value is different for different camera systems. The range of this distance, which will render an image clearly in focus within all focal lengths, is usually measured to a precision of hundredths of millimetres, and is not to be confused with depth of field.

Lenses can be adapted from one mount (and respective FFD) to another. FFD determines whether infinity focus can be accomplished with a simple non-optical adapter. Optics to correct for distance introduce more cost and can lower image quality, so non-optical lens adapters are preferred. A simple non-optical adapter holds the longer FFD lens the appropriate additional distance away from the sensor or film on the shorter FFD camera. A camera body with a shorter FFD can accept a larger number of lenses (those with a longer FFD) by using a simple adapter. A lens with a longer FFD can be more readily adapted to a larger number of camera bodies (those with a shorter FFD). If the difference is small, other factors such as the sizes and positions of the mounting flanges will influence whether a lens can be adapted without optics.

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Displacement prisms maintain the direction of the light beam, but adjust its relation to the normal. An example of a displacement prism is the simple rhomboid prism. This prism displaces the incident beam without changing handedness. The direction remains the same, so rhomboid prisms are ideal for binoculars, rangefinders, and laser instrumentation.

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An optical prism is a solid, transparent optic with flat surfaces which refract light. Light enters through one surface, and may be rotated, deviated, or dispersed before leaving through another surface. These surfaces are highly polished, and the angles between them, the number of surfaces, and the position of them determine the function of the prism.

Deviation prisms include half-penta prisms and Amici roof prisms. Amici roof prisms deviate the light path by ninety degrees while inverting the image, and are used in microscopes and telescope eyepieces. If the roof faces of the prism are coated the beam can be deviated by other angles as well. Half-penta prisms deviate the ray path by 45° and are used in Pechan erector assemblies.

A simple triangular prism is an example of a dispersion prism. Since the refractive index of light changes as the wavelength changes, Snell’s law tells us that the deflection angle of the light will change proportionally. For instance, red wavelengths (656.3 nm) are longer and will be refracted less than shorter wavelengths, such as green(587.6nm) or blue(486.1nm). This separates the colors/wavelengths of light as it travels through the prism. The dispersion a prism provides depends on its index dispersion curve and on the geometry of the prism. For spectroscopy and telecommunications, equilateral prisms are often used.

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Due to research on optimal flange focal distance settings, it is currently considered better for flange focal distance to be set to somewhere within the film's emulsion layer, rather than on the surface of it. Therefore, the nominal flange focal depth will be equivalent to the distance to the ground glass, whereas the actual flange focal depth to the aperture plate will in fact be ~0.02 mm less.

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Flange focal distance is one of the most important variables in a system camera, as lens seating errors of as little as 0.01 mm will manifest themselves critically on the imaging plane and focus will not match the lens marks. Professional movie cameras are rigorously tested by rental houses regularly to ensure the distance is properly calibrated. Any discrepancies between eye focus and measured focus that manifest them­selves across a range of distances within a single lens may be collimation error with the lens, but if such discrepancies occur across several lenses, it is more likely to be the flange focal distance or the ground glass (or both) that are misset.

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Avantier Inc. utilizes a variety of high-quality materials such as fused silica, filter glass, Germanium, Silicon, and ZnSe in manufacturing optical prisms. Their in-house coating facilities offer standard and custom coatings including anti-reflective designs, reflectors, beamsplitters, and coatings with high laser damage thresholds. This ensures optimal performance and durability across diverse applications.

Rotation prisms, such as dove prisms, rotate the beam of light and hence the image. Rotation prisms are used in pattern recognition, astronomy, and for imaging behind detectors or around corners. One type of rotation prism is the dove prism, which rotate the image by 180 degrees while creating a left handed image. Schmidt prisms deviate the ray by 45 degrees while creating a right handed image.

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But that’s not all. A right angle can also be oriented so as to be used as a dove prism, which produces a rotation of 180 degrees. Again, the image may be reverted or inverted depending on how the prism is oriented.

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Since optical prisms redirect light at a designated angle, they may be used to reflect light, to bend it within a system, to change the orientation of an image, or to break light up into it component wavelengths or polarizations. Isaac Newton used a simple prism to disperse a beam of white light into the full spectrum of component colors, proving that white light was in fact nothing but a combination of colors. This same dispersion technique is still used in spectrographs and refractometers. Optical prisms can also be used, in reverse, to combine optical beams into one.

Prisms may be divided into four main types: dispersion prisms, reflection prisms, displacement prisms and rotation prisms.

Now take the same prism, and orient it so that the light enters through the hypotenuse face.  This configuration has a special name; the porro prism. The ray’s direction will be reversed and the light beam will enter and exit from the same face. The image will be reverted or inverted, depending on whether the prism was upright or flat.

Typically, camera bodies with shorter flange focal distance can be adapted more readily to lenses with longer flange focal distance.