Originally posted by K1D27H Perhaps he said it that way because several of the DA* lenses actually cover full frame sensor (tested on film camera).
Film is much more forgiving that high resolution digital. Center quality would be high, but edge quality would be very poor, and AF points outside the center would be of little use.
Look at the test charts of the FA Limited lenses on APS-C sensors as posted on Photozone or Lenstips. Even on APS-C we see edge quality suffering. Now double the size of the sensor and you have a lens like a Sigma 30mm f/1.4 where the center sharpness is phenomenal, but everything outside the center is very soft and AF points are practically worthless.