Focal length - Wikipedia, the free encyclopedia
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The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (defocuses) light. For an optical system in air, it is the distance over which initially collima...
en.wikipedia.org/wiki/Focal_length
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When people refer to a lens as being 'fast' they are referring to the aperture, i.e. An aperture of F2.8 is faster than a lens with a max aperture F5.6. It makes the lens fast because you can use a faster shutter speed at F2.8 than you can ...
http://www.pixalo.com/community/cameras-lenses-accessor...
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Lens and Focal Length ... The important difference between the lens of a digital camera and the lens of a 35 mm camera is the focal length. The focal length is the distance between the lens and the surface of the sensor. ... Focal Length 35 mm Equivalent View Typical Uses...
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www.frogprints.co.nz/help/focal.cfm
www.frogprints.co.nz/help/focal.cfm
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Ars Technica Ars OpenForum 3.0b Audio/Visual Club Lenses:explain focal length, angle of view and crop factor relationships to me please ... If I have a 100mm focal length lens and I put it on my d350, it effectively becomes at 160mm due to the 1.6 crop factor. One thing I'm unsure of is what that is in terms of...
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episteme.arstechnica.com/eve/ubb.x/a/tpc/f/67909965/m/1...
episteme.arstechnica.com/eve/ubb.x/a/tpc/f/67909965/m/114009523731
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Binoculars are rated by magnification and diameter of the objectives ( the large light gathering lens ) so your 20 x 50 relates to a magnification of 20 times and an objective lens 50mm in diameter. ... To look at the moon you'll get lots of light so magnification is what you need, ... As with everything size is not all important,
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www.theanswerbank.co.uk/Science/Question104491.html
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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 (43.3mm) divided by the diagonal of the sensor.
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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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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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The first step on the path to getting the best lens for your new digital SLR is to decide what focal length you'd like. Don't know what focal length is? That's OK, we'll explain it. ... That's the textbook definition, but it really doesn't explain too much about why focal length is useful.
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www.digital-slr-guide.com/focal-length.html
www.digital-slr-guide.com/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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