So the camera is more or less finished. After using for a week or two I find I really miss a manual aperture stop. When using a 140mm F/3.2 from an old dia projector I can't set the shutter fast enough to avoid overexposing the images in daylight. This is because the Due can't A/D convert faster than about 300k samples/second without really complicating the code. 

So this is what I came up with:

Why limit yourself to round holes when you can have some fancy shapes instead? Now I just have to find a way to make it quick and easy to change aperture stops.