Zoom Question
Gareth Slee wrote:
I'm a complete novice to this so please excuse me. I have a CCTV camera and I'm trying to decide on what zoom lens to use with it. This is where things get confusing for this old brain of mine. I've seen two different zoom lenses at a local store. 6-72mm (x12 zoom) 8-80mm (x10 zoom) With everything else being equal which lens would make an object appear to be nearer? -- Gareth Slee Stupid gravity! Homer Simpson: (Falling out of treehouse) the 8 to 80. dave |
Zoom Question
Bay Area Dave wrote:
the 8 to 80. So the higher the second number, the nearer the image will appear to be? -- Gareth Slee Stupid gravity! Homer Simpson: (Falling out of treehouse) |
Zoom Question
Jim Townsend wrote:
All things being equal.. The longer the focal width, the narrower the field of view and the closer objects appear. Of the two lenses you listed, the 8-80mm lens provides the longest focal length and will provide the greatest magnification. Note that the X in zoom lens doesn't represent the magnifying power the way telescopes and binoculars do. The 'X' represents the difference between maximum and minimum focal length. The X of a zoom lens is determined by dividing the maximum focal length by the minimum. 72 / 6 = 12x (from 6mm you can increase the focal length 12x) 80 / 8 = 10x (from 8mm you can increase the focal length 10x) If they made a 2mm to 50mm lens, it would be a 25X lens, but wouldn't have near the magnifying power of the 8-80mm 10X lens.. Thanks Jim That's cleared it up. -- Gareth Slee Stupid gravity! Homer Simpson: (Falling out of treehouse) |
Zoom Question
"Gareth Slee" writes:
Bay Area Dave wrote: the 8 to 80. So the higher the second number, the nearer the image will appear to be? Yes, that's exactly the point. The maximum focal length the lens reaches will give you the biggest image. So the lens with the largest maximum focal length will give you the biggest image at its longest setting. The "x" number given sometimes for zoom lenses, x12 or x10 in your example, is simply the ratio of the longest to the shortest focal length. That tells you how much variation there is from one end to the other -- but nothing about how wide the wide end is, or how long the long end is. (I'm used to seeing it as "12x" rather than "x12", by the way). -- David Dyer-Bennet, , http://www.dd-b.net/dd-b/ RKBA: http://noguns-nomoney.com/ http://www.dd-b.net/carry/ Pics: http://dd-b.lighthunters.net/ http://www.dd-b.net/dd-b/SnapshotAlbum/ Dragaera/Steven Brust: http://dragaera.info/ |
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