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

Started Apr 17, 2011 | Discussions thread
noirdesir Forum Pro • Posts: 13,501
Re: noirdesir - thank you - one more question

edwardaneal wrote:

thank you for finally admitting that faster glass can have an advantage in lower light

Thank you for repeatably showing a severe lack of reading comprehension and for actively trying to mislead the others. It just makes me more confident that my earlier judgement about you was absolutely correct.

(For once I did not even say that faster glass makes CD-AF faster, rather that it likely makes AF slower because the additional hunting caused by low DOF is much more important than the reduced signal noise. Secondly, this whole discussion up until your previous post was about PD-AF, so I have not changed my statements regarding PD-AF, I just added a description of a different kind of AF system.)

so one more question

And are you willing to do a very simple thought experiment? (I highly doubt it but I am intrigued whether this is because you are unwilling to do something that might prove you wrong or whether you are simply incapable of doing it.)

if you open up the aperture of a lens doesn't it increase the light evenly across the frame?

if the light is brighter evenly across the frame wouldn't it also be brighter on the windows to the phase detect AF sensors?

If the light were brighter on these windows wouldn't it be easier for these sensors to detect contrast in lower light situations?

If you point two flash lights from different angles at the same spot on your wall, switching both on makes the spot brighter than switching on only one. If you now put a shield between one of the flash lights and the spot on wall but not between the other flashlight and the wall, it will not make any difference for the brightness of the spot on the wall whether the first flashlight is switched on or off.

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