Would somebody care to explain to me what this "f/8 AF limitation" is, please?
Does it mean autofocus won't work if you set your aperture smaller than f/8?
No, it just means that if your lens largest aperture is smaller than f/5.6 (next step is f/8 typically) it can't autofocus. Focusing is always made at largest aperture, the lens is stopped down to the target aperture when taking the picture.
Lenses don't have as small as f/8 natively, but with teleconverters you get it, 1.4x adds one stop, 2x two. So if your camera cannot do f/8 autofocus you cannot get autofocus with a 2x teleconverter on an f/4 lens or 1.4x on an f/5.6 lens, which can be a limitation for especially wildlife photography. 2x on 500/4 to get 1000/8 with autofocus can be a nice option to have. Or on the low end 400/5.6 => 560/8.
Excellent explanation. Thank you! I know understand and see what the problem could be. My f/2.8 lens would not have an issue, but an f/5.6 lens with a 2x teleconverter would. Not being able to use AF at that point would rather suck.
Thanks, understood and filed.