A solar filter sits between your lens and the sun, and it knocks down the light to 1/10000 or so of its original amount – something a camera can then deal with. If you’ve planned ahead far enough you may already have a solar filter. If not, you can improvise something like this one for $3.
Regardless of whether or not there's an eclipse going on, this would be a great easy project for educators. Ask the kids to bring in their own cups. One Mylar emergency blanket is enough to do tons of these little filters. Teach kids the safe way to observe the Sun - never look directly at it, but reflections, cameras, etc. are fine.
DO NOT LOOK THROUGH THIS FILTER AT THE SUN. YOU COULD EASILY BLIND YOURSELF.
I can’t stress the previous lines enough. This design is safe for cameras, not for eyes, because it blocks visible light. That leaves the harmful UV and infra-red rays unblocked – things your camera is not sensitive to, but your retinas are! If you want a visual (observing) filter, buy one. No DIY solution can be tested / guaranteed as a commercial one can.
Step 1: Materials
* Empty plastic food container (with lid), larger than lens
* Mylar sheet. Buy an “emergency blanket” from the camping supplies section at Wal-Mart. Total cost: $2.97
* Razor blade
* Black spray-paint