Jessica M. Pickin |
12x compared to 18x How do you figure out 12x compared to 18x when working with a non-SLR camera?
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Alan N. Marcus |
Hi Jessica, I will lay the basis of the math out for you, you can do the rest. Over the years the camera has evolved using the human eye as a model. Our eye brain combination yields an angular field of view of about 53°. The camera duplicates this angle of view when the lens employed operates at a focal length about equal to the diagonal measure of the film or chip employed. As an example the 35mm film camera uses film that measures 24mm height x 36mm length this computes to a diagonal measure of about 43mm. Most 35mm cameras sport a normal lens that is 50mm in focal length. This is a rounded up compromise. A full frame digital chip has the same diagonal measure. Most other digitals sport smaller chips. While their is no standard most are 66% or this value or about 28mm as to diagonal measue. Your digital camera likely will produce a normal angle of view when the lens used hovers around 28mm. Now the modern cameras sport a zoom lens which allows the user to change focal length. Shorter than 28mm is in the realm of the wide angle and longer is telephoto. Say your camera sports a zoom lens that tops out at 200mm focal length and bottoms out at 25mm focal length. The math is 200 divided by 25 usually written as 200 / 25 = 8x. Thus if your camera sports a zoom that tops out at 300mm and bottoms out at 20mm the zoom rage is 300 / 20 = 15x. Another aspect: Alan Marcus (beware I am known to provide marginal technical advice)
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Jessica M. Pickin |
Thank you for your help
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