AF design with compatibility up to f/8
I don;t think I can recall any previous AF being related to aperture and I'm trying to get my head around what the product brochure is describing:
I'd be interested to hear opinions and ideas on how this works in real world shooting and what considerations if any will need to be made at various f-stops. Or is this just a super telephoto feature as it crops down to such a narrow field of view?
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#1. "RE: AF design with compatibility up to f/8" | In response to Reply # 0briantilley Nikonian since 26th Jan 2003Thu 13-Sep-12 03:21 PM
Before the D4 and D800 were introduced, all Nikon's AF systems were officially rated to be effective at a maximum aperture of f/5.6 or wider (note that in practice, it was generally possible to have AF work with good light and a good target at apertures a little smaller than f/5.6).
All Nikon are saying now is that the AF system has been improved in the latest cameras, and will be effective (with some restrictions on AF point selection) at an aperture of f/8.
#2. "RE: AF design with compatibility up to f/8" | In response to Reply # 0stappy Nikonian since 06th Aug 2009Thu 13-Sep-12 03:24 PM
A lens aperture will be held open to its widest aperture for focusing and then stopped down just before shutter release. So, if you have a f/2.8 lens and taken an image at f/16 the focus system will use the f/2.8 for focusing and then stop down to f/16 for the shot.
Now, if you have a lens with a smaller maximum aperture, say 5.6, or if you use an f/4 lens with a 2x teleconverter which would give f/8 then the autofocus system has to operate with less light.
The spec is saying that a certain subset of the autofocus sensors are rated to operate with lenses that have a maximum aperture up to f/8. Many previous cameras were rated up to f/5.6.
Of course, ambient light conditions will have an impact.
#4. "RE: AF design with compatibility up to f/8" | In response to Reply # 3msullivan09 Nikonian since 01st Sep 2009Thu 13-Sep-12 05:42 PM
>Ahhhh - thanks for translating guys
Ditto. Very educational and explains why focus hunts even if the viewfinder doesn't seem to be excessively dark. Kind of like thinking you have money in the bank just because you have checks! Pretty good improvement.