This isn't good advice. People shouldn't build their own solar filters unless they have a very good understanding of the risks. The risks are significant, because you've got a lens pointing at either the eye (if you look through the viewfinder) or the CCD, and concentrated sunlight will quickly damage either.
I've purchased the sheet, cut it to size with my laser cutter, and installed in my own optics. The sheets quickly get scratched, and then you end up with intense spots or lines of light falling on the sensor (or your eye!)
Additionally, he suggests a screw-on filter. Don't do that- buy a cap filter with thumbscrews. You'll need to remove the filter quickly, and then put it back on quickly, when transitioning from partial eclipse to total (if you're in an area with only partial eclipses, the screw-on filter is OK because you'll never remove the filter).
I've purchased the sheet, cut it to size with my laser cutter, and installed in my own optics. The sheets quickly get scratched, and then you end up with intense spots or lines of light falling on the sensor (or your eye!)
Additionally, he suggests a screw-on filter. Don't do that- buy a cap filter with thumbscrews. You'll need to remove the filter quickly, and then put it back on quickly, when transitioning from partial eclipse to total (if you're in an area with only partial eclipses, the screw-on filter is OK because you'll never remove the filter).
I have multiple solar filters and the preferred kind is aluminzed glass, rather than aluminzed sheet plastic. It's pricey, but the safest and most reliable filter I've found is this: http://thousandoaksoptical.com/shop/solar-filters/full-apert...