Using Solar Filters for Cameras
Solar filters are used in astrophotography to help obtain the best shots of the sun, protect the lenses, protect the camera, and to protect the operator's eyes. The filters are designed to absorb the ultra violet, visible and infrared energy of the sun. Neutral density and polarizing filters can help reduce light, but if you are photographing the sun, then these filters will not provide adequate light reduction or protection to your eyes. You must use professional solar filters.
How a Solar Filter Helps Protect the Camera
The sun is a very bright light, and when that light is focused through the lenses and into the camera, it can cause a lot of damage. Holes can be burned into the shutter and the leafs can become warped. This is damage that will make your camera unusable, and you would most likely forced to buy another one because it will cost more than the camera's worth to fix it. A solar filter will reduce the heat and light passing through the lens, which offers some protection to your stuff. However, it's always a good idea to aim the camera away from the sun when you're not using it.
How a Solar Filter Protects Your Eyes
As said before, the sun is very bright. Looking at it without any protection to your eyes can cause temporary blindness. ND filters reduce light, but the direct sun is so powerful that they won't really be that helpful. In fact, it won't offer you any protection all. You need a solar filter to do the job. With a solar filter on the lens, you'll be able to look through the viewfinder to find your shot without harming your eyes. If you're not using a solar filter, then do not look through the view finder when the camera is pointed at the sun.
How a Solar Filter Helps Exposure
The sun is far brighter than the dynamic range of any camera with a closed aperture at the lowest ISO setting. A solar filter reduces the light that passes into the lens, which means that the sun will end up looking like the sun with it's details visible instead of a giant white blur.
Using Solar Filters
Solar filters can be screwed on to your lens just like any other filter. Keep them clean with the proper cleaners and avoid getting them scratched. Use them only when you're photographing the sun. When properly cared for, these filters can last for decades.