A friend of mine today gave me this video lamp that she found while cleaning the basement:

http://img505.imageshack.us/img505/830/lamp10sq.jpg
http://img427.imageshack.us/img427/7894/lamp27an.jpg

The reflector part with the bulb can be rotated about 120 degrees up and down.

It has no bulb, but specs on the back say that the bulb should be 1000W. It is also written that the lamp should not be used longer than 5 minutes. After that it should be switched off until it cools down.

Before spending money for a bulb, I am wondering for what could this lamp be used with this 5 minute limit. Would it be useful for indoor filming so that it is directed to the white ceiling (like using bounce flash in photography)?

I don't think anything with a 5 minute limit will be very useful in video production.
If I got that warning I'd probably ignore it (not suggesting that you do, just saying I would).
It could be the bulb gets too hot and could melt something in which case I wouldn't use it at all. You could try a lamp that's a lower wattage (500 or 250) if it fits - it looks like it uses regular worklight lamps you can get at a hardware store and if you can get it working, the fact it can tilt and has a tripod mount would make it really useful as a video light.

it looks like it uses regular worklight lamps you can get at a hardware store and if you can get it working

That was the first thing I tried when I got it, but found out that the bulb should be 12,5 cm long, what is more than regular worklight bulb.

I think it should be this one:
http://www.svetila.com/eProdaja/product_info.php?currency=EUR&cPath=66_69&products_id=653

Unfortunately, this store (I don't know for any other in Slovenia selling pro light equipment to end users) has only 1000W bulb. I'll probabily buy it and give it a try...

I have a lamp like this that uses the DYH600 lamp. This is a leftover from the days of 8mm home movie cameras. Those things needed lots of light. My uncle used to do 8mm movies and it would blind you to look in the camera directly. Like yours, the head on mine tilts up and down so you could bounce it off the ceiling if need be. The 5 minute limit is to maximize bulb life. I have some DJ lighting that uses quarts lamps where they recommend 10 minute runtimes.

Most times in shooting 8mm movies, you wouldn't be running the camera for much more than 5 minutes at a time anyway.

My lamp was one that was being sold in the early days of VHS camera/recorders (that's when I got it) but was originally for 8mm movie cameras. They hadn't designed lights specifically for home video cameras at that time.

-gb-