Quote Originally Posted by another view
ND400? I've seen them come up on ebay from time to time. Like Chunk says, it could be interesting for daylight shots - along the lines of a pinhole except different (very different, OK). How many stops does that work out to?

So with an ND400, it's safe to look thru the camera at the sun with a long lens?

Yes, it is safe to look at the sun with a ND400. That's why they make them. The ND400 drops the light by 9 stops. That works out to about 1/500th the light level. You have to drop the sunlight to at least 1/100th of it's intensity to make it safe. That works out to about 7 stops. I think 7 stops actually works out to 1/125th. I guess they'd rather be safe than sorry with their ND400.

A good solar filter (ND400 or other) is a nice thing to have. You can use it to take photo's of sunspots, solar eclipses, and transits of Mercury and Venus. I've got a solar filter for my Celestron C-8, and I've used it to take photo's of the large sunspot group we had last year. It was the largest sunspot group in many years, and the sunspots were larger than the Earth!