[Jose]

Canon makes an issue of telling the user that this flash "automatically recognizes EOS Digital camera's image size and automatically sets the flash coverage for lens focal lengths from 24 to 105 mm."

When I use the flash with Canon EOS 1Ds MKII with a 16-35 mm L II it reads from 35 to 24 and if I go beyond 24 still reads 24. Fair enough, they tell us about this.

When I use the flash with a Canon 40 D and the same lens it still reads from 35 to 24. But then this lens is actually approximately a 25 to 50 mm when used with the 40D. Why would not the flash read from 24 (close enough to 25) to 50 mm?