Intense curiosity finally got the better of me today (May 3, 2006), so I set up my Sigmonster with 16x worth of teleconverters. That's a focal length of about 12.8 meters, or almost 42 feet, before crop factor. This is equivalent to about 256x magnification (if 1x = 50 mm), and an angle of view of 20,488 mm on the 350D.

Yup, the camera functioned ok at this focal length and aperture (f/91 wide open). Shooting in direct mid-morning sunlight, the view finder is just a bit brighter compared to having the lens cap on. Manual focusing is a breeze, as easy as reading a newspaper in complete darkness. My attempts to control shake at this length (effectively about 0.12 degree or 7 minutes angle of view) merits a Medal of Valor in my opinion. I didn't try to tape the pins on the TCs and see if AF would work.

All in all, the photo taken at 12800 mm f/128 (one stop from wide open for "better image quality") is recognizable, but I seriously doubt any practical application.