I'm convinced this is a physical filter that moves completely in. I zoomed all the way in and put a rectangle HDV-Z96 LED light facing slightly off to the side facing into the lens. When I went one click past f/4 I could see a reflection of my entire rectangle light appear. When I went back a click the light reflection disappeared. It appeared to be a filter rotating from the bottom up to cover the opening completely. As I continued to increase the f-stop the iris didn't appear to change size so I'm wondering how they're handling the continuous change.

We have a WINNER! I checked it out and yes, you are right. I admit defeat, it is a rotating filter very close to the iris.

Sorry for the trouble, but it was a very interesting debate.

It is time to change the subject;
What type of internal memory does the Canon xa 10 use? is it a Hard drive or is it solid state memory?

Just one last thought on the ND filter subject.

It would be nice if canon made the ND filter setting independent from the F stop value. I love to record with a open iris and a shutter speed between 1/25 and 1/120.

With the auto ND filter it is difficult to expose in very bright light conditions with a open iris and without having a ridicules shutter speed.

It would be nice if canon made the ND filter setting independent from the F stop value.

All it takes is a bit more money for a step-up camcorder. However, you can still add an external ND filter.

Rainer, Don's correct. If you buy a camcorder with no manual ND filter switch on the body then you can bet your boots that it has undocumented, unavoidable and constantly operating internal ND. This hidden ND isn't there to confuse or distort your aperture readouts (though it does of course), it's there to give you sharper pictures, while keeping to sensible (movie-making) shutter speeds.

Of course cameras like the GoPro couldn't care less about using 'proper' shutter speeds, so they abandon the complex and expensive internal ND solution and simply control the exposure in the aperture priority mode - by varying the shutter speed per frame. In bright sunlight 1/1000th sec is not uncommon, giving the footage that staccato look.

tom.