The EOS-3 manual says that the central focusing point is capable of crosstype focusing with EF lenses having a maximum aperture of f/4 or greater. My EOS-3 with a zoom lens like the 28-135mm f3.5-5.6 is not capable of crosstype focusing in the central focusing point when the zoom is set in the lower range (28mm to 45 mm) where the maximum aperture is 3.5 or 4.0. Only the horizontal component works. The same is true for the 28-105mm f3.5-4.5. The crosstype focusing works fine with my 300mm f/4 and 17-35mm f/2.8.

Is this a mal-function in my EOS-3 or is it just the normal thing for variable aperture zoom lenses mounted on the EOS-3?

-- Allan Hansen (alhans@get2net.dk), March 28, 2000

Answers

Allan,

The EOS 3 crosstype focusing is based on the maximum aperture. In your case for the f3.5-5.6,it is the aperture f5.6 that will be used for the focusing censor.

-- Philip Hua (philip_hua@ml.com), September 26, 2001.