The canon 35mm lens is twice faster than the Sigma 30mm.

Am I using "twice faster" in that sentence correctly? It doesn't sound very right to me.

Hello Mountain,

Try "twice as fast."

(But what is it faster at? Auto-focus? Something else? I don't think of lenses as moving, so "faster" sounds odd without a context.)
Twice as fast means two times as fast. It does mean that it is faster.

As fast on its own (without the twice) would mean equally fast.
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I don't think it should be "twice as fast" because it would imply it as equal as fast not faster and yes, I'm refering to the auto focus. Please correct me if I'm wrong. Thanks
 nona the brit's reply was promoted to an answer.
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