Quote Originally Posted by Alan


But, something that I didn't expect was the extender didn't affect the aperture setting.


The 100-400 still showed f/5.6 at its longest length and the 300 f/4 still showed f/4. I took a couple of shots from each lens and the file info confirms it.


The aperture is affected. That's physics. The reason the file info 'confirms' that the aperture is not affected is the same reason autofocus works - the tape blocks the pins that transmit aperture data to the lens. The camera 'doesn't know' that the 100-400mm is at f/8, so it 'assumes' the lens is f/5.6 based on stored lens data for that focal length. It autofocuses accordingly and stores that (incorrect) EXIF data with the image.