Why is f/1.8 called fast?

Started Dec 1, 2013 | Discussions thread
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AlphaTikal
AlphaTikal Senior Member • Posts: 2,097
Why is f/1.8 called fast?

I don't get it. Why is a lens called fast, if the wide open aperture is meant? I mean, a lens can be fast, if the AutoFokus is fast.

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Sony RX100 Sony a77 II Sony DT 16-50mm F2.8 SSM Tamron SP 90mm F2.8 Di VC USD 1:1 Macro (F004) Samsung Galaxy S7 edge +11 more
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