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Crown glasses such as BK7 have a relatively small dispersion (and can be used roughly between 330 and 2500 nm), while flint glasses have a much stronger dispersion for visible light and hence are more suitable for use as dispersive prisms, but their absorption sets on already around 390 nm.
AI lenses enabled lenses to be mounted without having to align the lens with the camera body's "rabbit ears". The F2AS Photomic (DP-12 head) was the most advanced F2 version and the chrome version with Nikkor AI 50 mm f/1.4 lens had a US list price of $1,278 in 1978.
Lenses made with fluorite are superior to fluoro-crown based lenses, at least for doublet telescope objectives; but are more difficult to produce and more costly. [36] The use of fluorite for prisms and lenses was studied and promoted by Victor Schumann near the end of the 19th century. [37]
Lens designs more complex than achromatic can improve the precision of color images by bringing more wavelengths into exact focus, but require more expensive types of glass, and more careful shaping and spacing of the combination of simple lenses: apochromatic lenses bring three wavelengths into a common focus and requires costly materials
The wedge prism is a prism with a shallow angle between its input and output surfaces. This angle is usually 3 degrees or less. Refraction at the surfaces causes the prism to deflect light by a fixed angle. When viewing a scene through such a prism, objects will appear to be offset by an amount that varies with their distance from the prism.
A relatively new type of telescopic sight, called prismatic telescopic sight, prismatic sight or "prism scope", replaces the image-erecting relay lenses of a traditional telescope with a roof prism design commonly found in compact binoculars, monoculars and spotting scopes.