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

Started Apr 17, 2011 | Discussions thread
noirdesir Forum Pro • Posts: 13,561
Re: I asked Nikon - and they say it is bad information

edwardaneal wrote:

I just e-mailed Nikon about an hour ago - this is what I asked them

"I was recently told by a camera store that Canon DSLR's have special auto focus sensors that allows them to take advantage of the extra light and contrast provided by lenses with apertures that are f/2.8 and faster. I was also told that Nikon DSLR's do not have any sensors like this and will not auto focus any better in low light with an f/2.8 lens than they will with an f/5.6 lens

Can you please tell me if this is true

Thank you"

this is the reply I just got

" Subject
Fast lenses

Discussion Thread
Response Via Email (David D.) 04/27/2011 04:14 PM

Thanks for the question. It sounds like you got some pretty bad info! I'd guess what you were told is related to the difference between cross-type and line-type AF sensors. In an autofocus system some of the spots use cross type sensors (which are what it sounds like, two sensors that cross) and some sensors are just a single line.

A cross-type sensor is generally better because it can focus on a subject that has horizontal and vertical contrast while a line type is best for just horizontal subjects.

In some model Canon cameras (their lower end I believe) they have more cross type sensors than our comparable cameras but only the center AF point benefits from the faster lens in their system

Of course there is so much more to performance than the type of AF sensor that all of this is really just speculation since the camera's CPU, lens CPU, lens motor, actual subject, lighting condition, etc are really what determine performance.

I hope this helps.


Thanks for using Nikon products!
Nikon Inc. (USA) Support / Service
http://support.nikontech.com "

sounds to me as if David is saying that Nikons AF does in fact benefit from faster lenses and the following comment: "only the center sensor benefits from faster lenses in their system" sure makes it sound to me like he is saying that with Nikon you dont have this limitation.

He tries to create that impression without actually saying it (and mainly tries to move away the discussion from that issue by talking about cross sensors and how the overall system is what counts). Any Nikon representative would avoid at all cost to admit that a competing system is better in some regard, so evasive answering is to be expected.

There have been a lot more people before you who have tried to get an answer about that issue from Nikon, all of them got this kind of evasive answer. As others and I have said repeatedly, only Canon is willing to unambiguously go on the record about f/2.8 AF sensors.

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