Yes, I believe the size of the cmos AF chip determines the max spread of the AF points. To have AF points covering the entire viewfinder would require a AF chip the size of the imaging sensor.
According to Chuck Westfall, it\'s an angle of illumination thing, with degrees off-axis being the limiting factor. He has an explanation on his monthly question-and-answer column on www.digitaljournalist.org
Sep 18, 2008 at 06:06 PM
Previous versions of RDKirk's message #6183511 « Canon 5D Mark II master thread »
