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Author Topic: canaon lens designations  (Read 2637 times)

Stickbowhntr

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canaon lens designations
« on: September 13, 2006, 05:45:45 pm »

Can anybody help me decide on a lens for my new toy. I can not find what the III USM Autofocus, III Auto Focus, usm Autofocus and UsM II are all about. I want something for outdoors nature landscape and something for indoors/sports like college basketball/volleyball ? I need something for just getting started and a lower cost for my budget right now untill  I know better what it is I realy need.
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dobson

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« Reply #1 on: September 13, 2006, 06:23:46 pm »

USM refers to the high-speed autofocusing motor in the lens. The roman numerals II or III refer to releases of the lens (often just cosmetic differences).
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dobson

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« Reply #2 on: September 13, 2006, 06:41:44 pm »

I forgot to mention that when shooting indoors (especially action), you want a reasonably "fast" lens. The speed of a lens refers to the F-number, or aperture size. The lower the number the more light gets in allowing you to use a faster shutter speed especially in low-light situations. Unfortunately even small increases in aperture size can dramatically increase price.

One option for those on very tight budgets is the EF 50mm f/1.8, this lens has a "normal" focal length and is very good optically for the price. Just don't expect much in the way of build quality or AF performance. You get what you pay for.
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mbutler

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« Reply #3 on: September 13, 2006, 07:40:45 pm »

Hi,

The best Canon autofocus motors are the ultrasonic (USM) ring type. These are identified by a gold ring on the prosumer lenses such as the 85/1.8, 50/1.4, 100/2.8 macro, etc. They're also on all the red-ringed L lenses. The chief advantages are that USM is fast and quiet and allows manual focusing even when the lens is set to auto focus.

Some of the consumer lenses in the 28, 35, 50 focal lengths use an older autofocus technology that is rather clunky and noisy, not a big hindrance for landscapes but a disadvantage for sports and other fast-moving situations. You can also inadvertantly damage one of these lenses by manually focusing it in in autofocus mode.

Hope that helps a little.
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AdrianW

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« Reply #4 on: September 14, 2006, 02:34:42 pm »

The answer to all your Canon lens questions, and more is:
Photonotes FAQ/Lenses
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dobson

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« Reply #5 on: September 14, 2006, 03:41:12 pm »

That is an incredibly useful article. I'll have to keep it in mind if anyone else needs help.
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