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

Started Apr 17, 2011 | Discussions thread
Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 13,233
Re: Clarifications

noirdesir wrote:

With todays focusing screens, you won't see much if any benefit from lenses faster than f/2.8 (or maybe even f/4 with some cameras).

In the Nikon range generally changes in depth of field and screen brightness are observable at f2.5 and smaller on FX and f2.8 and smaller on DX.

I have yet to encounter a Nikon body where the screen does not look brighter between f4 and f2.8

Anything faster than f/5.6 (or probably f/5) is lost on the phase-detect AF (except on some Canon bodies which have a few special f/2.8 focus points). The phase-detect AF sensor in all Nikon bodies only sees light coming from the 'f/5.6 ring'.

I am sure this is an internet myth.

Nikon do not mention a limit. Those of us with a range of Nikon lenses find in general f4 focuses faster than f5.6, f2.8 focuses faster than f4, and f2 focuses faster than f2.8.

This could not happen if phase detect limited AF speed to no faster than an f5.6 lens
Leonard Shepherd

Good photography is mainly about doing simple things well. The challenge is doing simple things well enough for good results.

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