If shooting at f/22, is a fast 1.8 lens still considered fast?

Started Apr 17, 2011 | Discussions thread
noirdesir
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And Wikipedia is wrong in this regard
In reply to edwardaneal, Apr 22, 2011

edwardaneal wrote:

http://en.wikipedia.org/wiki/Autofocus

The speed of the AF system is highly dependent on the maximum aperture offered by the lens . F-stops of around f/2 to f/2.8 are generally considered optimal in terms of focusing speed and accuracy. Faster lenses than this (e.g.: f/1.4 or f/1.8) typically have very low depth of field, meaning that it takes longer to achieve correct focus, despite the increased amount of light.

And Wikipedia unfortunately is wrong in this. Notice that it gives no technical explanation of how phase-detect AF works at all. No technical explanation as why things are as it claims them to be.

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