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

you are wrong - - the quote is from here


and it is a writeup on the advantages of their f/1.4 lenses - in makes no mention of any specific canon body or any specific af feature. it only states that faster lenses increase contrast in low light. As I undrstand it higher contrast always makes it easier for the AF system to do its job even if there arent some special sensors.

As a side note what makes you think that Canon has some special thing in their sensors that Nikon does not have? from everything I have read these special sensors are just strategically placed cross type sensors that are only active with fast glass. Nikon allows all of its cross type sensors to be active regardless of the speed of the lens used so why would you think that Nikon had not placed any of these in locations to also take advantage of fast glass?. I have never heard Canon tout this as something only they have - dont you think they would? And if it really was something special dont you think Nikon would have matched it by now? Heck considering the fact that Nikon seems to have the better / more accurate AF system it would seem they have done better.

Anyway you can keep trying to convince me that all of the sources I have posted are wrong, but until you come up with something more credible I am going to have trust


and this

and this

and this

all of which either flat say you are wrong or demonstrate you are wrong in a controled test.

nothing personal but I have to go with the more creible sources that actually list references

also I notice that you did not addres my question if faster glass would have an advantage when using live view - as you know in live view the actual sensor is used for AF and it is a contrast detect system. It would seem obvious that faster apertures would allow more light and would clearly help when using live view.

So even in the extremely off chance that you are right about fast apretures and phase detect autofocus fast glass would still be a big advantage using live view in low light

So why would you post here that it has no advantage at all as you have?

Even if faster glass only had an advantage in live view mode it is still an advantage and replying to the OP that faster glass can help with AF in low light is a very valid statement.

so in the end - this is how it is - faster glass can improve AF performance. Will it always improve it - of corse not, but under certian conditions it will - - - and that my friend is a fact.

SteveL54 wrote:


The Canon marketing source you quote is refering to the f/2.8 advantage designed into their AF system.


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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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