Cimark MC Auto 28mm f/2.8 Pentax K-Mount Close this window to return to eBay Specifications Construction Infra-red Index

  The 28mm lens is considered to be an wide-angle lens. It is a great lens for shooting in congested areas, for creating or enhancing the depth of a subject.  Once considered ultra-wide, it is now a compulsory component in a well equipped system.  This lens produces images that include the view that we normally recall about a scene even though our actual angle of view is narrower.  Compared to a 50mm "normal" lens with a 46 degree angle of view, this lens nearly doubles the width of the scene captured from the same vantage point.  Straight lines do not appear curved as they would with a "fish-eye" lens. When making a photograph with the camera level the scene will appear very normal but with a great deal of depth. Due to the wide angle coverage that this lens provides, the multi-coating is indispensable in preventing undesired flare, ghost imaging and reduction in contrast often associated with conventionally coated optics.

Specifications | Construction | Infra-red Index

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Construction

	In the beginning, lens design required logarithmic tables, slide rules- and great patience. It often took three competent designers several years of steady work to complete the computation of a single 4-element lens. Today the modern electronic computer equipment performs extremely complicated calculations very rapidly and with great accuracy.
Fine optics alone cannot make a superior lens; the mechanical components are equally important. Lens barrels are precision machined for accurate positioning of all elements. Tolerances are so tight you have to break a vacuum to disassemble some elements. All mechanical components are precision machined to microscopic tolerances. Specially lubricated, wear-resistant metals assure consistently accurate apertures year after year.
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Infra-Red Index

When taking infra-red photographs, the focal point shifts slightly, and therefore, the lens must be extended accordingly. The difference varies depending on the lens, and it is indicated by the small "R" index or short orange line. In infra-red photography, use this infra-red index. First, focus your lens on your subject. Determine the lens-to-subject distance from the distance scale. Then match your "R" mark by turning the distance scale accordingly. Like the photo at left, if your subject is in focus at infinity, turn the distance ring and move infinity mark to the "R" index. Also, remember to use an R2 (red) or O2 (orange) filter and special infra-red film in this special photography.

Specifications | Super-Multi-Coating | Construction | Fixed-Focus Mark | Infra-red Index Close this window to return to eBay Click or the [ BACK ] button on your browser to return to the previous page.

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