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Old Dec 29, 2010, 5:25 PM   #1
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Default What lens?

Wanted to know info about lens. Can wide angle lens zoom or telephoto just for zooming only?
Some wide angle lens have 8-16mm F4.5-5.6 DC HSM others have 30mm F1.4 EX DC HSM. Telephoto lens have 50-500mm F4.5-6.3 APO DG OS and 800mm F5.6 EX APO DG HSM. Some just have a fix number. What does the focal length means? What does the number represent?
Can someone please explain the function and its purpose of the lens below. Do I need filters and why? Thank you very much.

Fisheye Lenses
Wide Angle Zoom Lenses
Wide Angle Prime Lenses
Standard Zoom Lenses
Standard Prime Lenses
Multipurpose Zoom Lenses
Telephoto Zoom Lenses
Super Telephoto Lenses
Macro Lenses
DC Lenses
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Old Dec 29, 2010, 6:32 PM   #2
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Very quickly, a zoom lens allows you to change focal length of the lens. It doesn't matter if it is 10-20mm or 300-800mm, they are both zoom lenses. What is difference is that the initial is a wide angle lens, the latter is a telephoto lens.

For an explanation of focal length take a look at http://www.whatdigitalcamera.com/tec...explained.html

As it sounds like you are right at the start of your photographic life then forget filters for now, there is a load more that you need to learn before adding them into the mix.
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Old Dec 29, 2010, 6:49 PM   #3
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The focal length is a physical property of a lens. The shorter the focal length, the greater the ability of a lens to bend light, so the wider its angle of view will be.

Some lenses have fixed focal lengths, and are often referred to as "Prime" lenses. Some lenses have adjustable focal lengths, and are often referred to as "Zoom" lenses. This is because, as the focal length changes, so does the angle of view, and when looking through the lens, you get the perception of "zooming" into a scene. (Note that there is a common misperception that "zoom" lenses are lenses with long focal lengths and thus, narrow angles of view. Zoom lenses can have any focal length.)

Wide angle lenses are lenses that have angles of view that are wider than the angle of view we perceive with our eyes. Wide angle lenses can be either zoom or prime lenses. Wide angle lenses try, often with great success, to maintain the rectilinearity of the scene. That is, straight lines in the scene will be straight in the photograph.

Fisheye lenses are lenses with wide angles of view, but don't project a rectilinear image.

Standard lenses are lenses that have angles of view that closely approximate the angle of view we perceive with our eyes. "Standard" is actually a misnomer. At one time, a "Standard Lens" was the lens that came with a camera, which just happened to have a "Normal" angle of view. Today, we refer to "Standard Lenses" as "Kit Lenses" because they come as part of the camera's kit. Technically, the correct name for these lenses is "Normal Lens" because they have a normal angle of view.

Telephoto lenses are lenses that have very narrow angles of view, so distant objects appear quite close.

Multipurpose lenses are lenses that have significant zoom ranges, and can serve as everything from a moderate wide angle lens to a moderate telephoto lens.

Super Telephoto lenses are lenses with very narrow angles of view, so very distant objects appear quite close.

Macro lenses are lenses that are capable of focusing on objects that are quite near to the camera, making very small objects appear quite large in the photograph.

DSLRs commonly use either of two size image sensors. One is the same size and shape as the exposures created by 35mm film SLRs. (These are often referred to as 'Full Frame' dSLRs.) The other is about 1/3 smaller, which makes it about the same size as the "C" format of the Advanced Photo System. (These are often referred to as 'APS-C' dSLRs.) The smaller APS-C sized image sensor allows the camera to be smaller, lighter and less expensive. Lenses intended for 'Full Frame' dSLRs will work fine on APS-C dSLRs because they project an image that's big enough for the larger sensor, and so will cover the smaller sensor, but lenses intend for the smaller APS-C image sensor don't project an image large enough to cover a 'Full Frame' image sensor. DC Lenses are Sigma's line of lenses that are intended for the smaller APS-C image sensors, and so are smaller, lighter and less expensive than their 'Full Frame' lenses, and won't work as well on 'Full Frame' dSLRs, if at all.

Teleconverters (sometimes called "tele extenders") are lenses that fit between a regular lens and the camera body, and multiply the focal length of the lenses they're used with. Sometimes, Conversion lenses are referred to as teleconverters. Conversion lenses are lenses that attach to the end of a regular lens. Teleconverters always make the focal length longer (hence, the "tele-"), but some conversion lenses are designed to make the focal length shorter.
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Last edited by TCav; Dec 29, 2010 at 7:03 PM.
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