To clarify, I know what an ND filter does. But I'm new to video cameras, and want to find out what the reason is behind how the electronic filter on the XF100 works. When you have it set to automatic, it automatically flips on when you get up to F4, and lets you cycle through a few densities for each aperture above that. But why can I not turn on the ND filter at a wide open aperture, like f2.8? I was using the camera today really for the first time, and it was a run and gun situation. Had a lot of bright natural light inside, and really wanted to open the iris up a lot to take full advantage of DoF. But of course, I could only open up so far until I started blowing out the image, and this was with -6dB gain. Is there a reason why you can't use ND with large aperature sizes on this camera, or are all cameras like this?