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Unformatted text preview: distortion called curvilinear . Straight lines may curve and parallel lines may converge. Telephoto lenses have longer focal lengths, 50mm > . They bring your subject closer to you in viewpoint and tend to compress distances between objects. This is a type of distortion called compression . You will notice a narrower angle of view also. Aperture numbers are ratios relating the focal length to the actual diameter of the diaphragm opening. The formula is: f# = Focal Length / Diaphragm Diameter Example: a 100mm lens set at an opening of 25mm has an f# of 4 (100/25 = 4). Lens with larger aperture openings are called fast. Smaller apertures sizes are called slow , capturing less light....
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- Spring '11
- normal focal length