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

Started Apr 17, 2011 | Discussions thread
edwardaneal Veteran Member • Posts: 9,101
Re: tell me Steve

I dont have to explain the f/1.4 results - they do - f/1.4 lenses have a much shallower DOF and require a more accurately adjusted camera AF system. having the extra contrast does not help if the af system lacks the precision to nail focus every time

if you look at one of my prior posts you will find a link to a description of the Canon af system it points out that that the AF system knows when a fast lens is mounted and moves in finer / smaller increments in order to deal with the smaller DOF of fast glass. This has nothing to do with using special sensors it just means the system makes finer adjustments in an attempt to improve focus accuracy.

You may also be aware that ALL of nikons new f/1.4 primes focus much slower than the F/2.8 AFS zooms for the same reason.

so as higher focus precision is required due to shallower DOF focus accuracy falls off - - - is that really such a shocker?

Anyway Steve - I hope you have a great evening - the debate has been fun

SteveL54 wrote:

The person doing the test doesn't understand the fundamentals of PDAF. Explain the f/1.4 test results. He is assumming a certain cause and effect.


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My kit - D200, 10.5mm f/2.8D, 35mm f/1.8G, 50mm f/1.4G & 70-300VR
SB800, SB600 and other misc lighting equipment

Lenses worth mentioning owned and sold– 12-24 f/4, 17-55 f/2.8, 35-70 f/2.8, 80-200 f/2.8, 20mm f/2.8, 35mm f/2, 50mm f/1.8, 50mm f/1.4D, 60mm f/2.8D, 85mm f/1.8, 105mm f/2D-DC, 180mm f/2.8, 300mm f/4D-ED

 edwardaneal's gear list:edwardaneal's gear list
Sony Alpha NEX-7 Sigma 60mm F2.8 DN Art Carl Zeiss Touit 1.8/32
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