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Principal Focal Length ... The principal focal length of a lens is determined by the index of refraction of the glass, the radii of curvature of the surfaces, and the medium in which the lens resides. It can be calculated from the lens-maker's formula for thin lenses.
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hyperphysics.phy-astr.gsu.edu/hbase/geoopt/foclen.html
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Focal Length The focal length of a lens determines its angle of view, and also how much the subject will ... ... The focal length of a lens determines its angle of view, and also how much the subject will be magnified for a given photographic position.
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www.photoaxe.com/understanding-the-lens-focal-length-an...
www.photoaxe.com/understanding-the-lens-focal-length-and-aperture/
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In other words, focal length equals image distance for a far subject. To focus on something closer than infinity, the lens is moved farther away from the film. This is why most lenses get longer when you turn the focusing ring.
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www.paragon-press.com/lens/lenchart.htm
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Focal Length Multiplier Optical Glossary Learn Digital Camera Digital Photography ... Focal Length Multiplier; By Vincent Bockaert; ... A 35mm film camera would require a lens with a longer focal length to achieve the same field of view. Hence the term Focal Length Multiplier (FLM). The FLM is equal to the diagonal of 35mm film...
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www.dpreview.com/learn/?/Glossary/Optical/Focal_Length_...
www.dpreview.com/learn/?/Glossary/Optical/Focal_Length_Multiplier_01.htm
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Focal Length Optical Glossary Learn Digital Camera Digital Photography ... In 35mm photography, lenses with a focal length of 50mm are called "normal" because they work without reduction or magnification and create images the way we see the scene with our naked eyes (same picture angle of 46°). Wide angle lenses...
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www.dpreview.com/learn/key=focal+length
www.dpreview.com/learn/key=focal+length
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Lenses and Optics ... Unless you're testing and calibrating lenses, I'm not sure why you'd want to know the exact focal length of a lens other than simply to satisfy your curiosity. It's just something that some people want to know. If you pay for a 400mm lens, it's nice to know you have a 400mm lens, not a 370mm lens I guess.
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www.bobatkins.com/photography/technical/measuring_focal...
www.bobatkins.com/photography/technical/measuring_focal_length.html
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Focal Length Defined ... When parallel rays of light strike a lens focused at infinity, they converge to a point called the focal point. The focal length of the lens is then defined as the distance from the middle of the lens to its focal point.
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www.photoxels.com/tutorial_focal_length.html
www.photoxels.com/tutorial_focal_length.html
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alculate Object Dimension, Object Distance, Focal length ... Enter Focal Length " " by millimeters millimeters ... Focal Length Calculation; Enter 2 figures in the column and click "calculate".
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www.canon.com/bctv/calculator/calculator3.html
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