[Jose]

What I am trying to say is that the 580EX II claims that it adjust automatically to the digital camera sensor in use but this not appear to be correct. As the size of the sensor in the camera changes so does the focal lens of the camera in use. As explained before, using the 16-35 mm with a Canon 40D it becomes a 25.6-56 mm. When using this combination and zooming to 35 mm, the flash zoom adjust to 35 mm; I maintain that it should adjust the zoom to the 50 mm. Using the 40D in P I shot the images below as set by the camera (both with identical f stop, shutter speed and ISO) but shot one as set by the flash zoom at 35 mm and then manually change the zoom to 50 mm. And there is a difference (disregard that both images were out of focus, underexposed and the presence of a hot spot--other topics of discussion). The first image was shot with the flash zoom at 35 mm and the second at 50 mm. It is obvious to me that with the flash zoom in the 50 mm the image exposure was better. I did not manipulate this images in any manner when converting to jpeg format from RAW.