I know this has been asked before, but it looks like there is some inconsistent info on this topic.

How does the brightness of a lamp / bulb change over time?

Theory 1: Start at 100%, go to about 80% after 100 hours, then travels down to 50% until lamp is about to die, goes down to 20% quickly

Theory 2: Start at 100%, go to about 50% after 100 hours, ramp down to 20% until bulb dies

Which is more accurate (or something else?)

... Altan

P.S. I'm wondering about this because I'm considering a projector (Black Pearl, Panasonic 2000u, Z2000) for a 108" 16:9 diag screen.

I know this has been asked before, but it looks like there is some inconsistent info on this topic.

How does the brightness of a lamp / bulb change over time?

Theory 1: Start at 100%, go to about 80% after 100 hours, then travels down to 50% until lamp is about to die, goes down to 20% quickly

Theory 2: Start at 100%, go to about 50% after 100 hours, ramp down to 20% until bulb dies

Which is more accurate (or something else?)

... Altan

P.S. I'm wondering about this because I'm considering a projector (Black Pearl, Panasonic 2000u, Z2000) for a 108" 16:9 diag screen.

Many bulbs are rated in hours to 50%. I don't know about getting down to 20% as I have replaced mine before it gets to that.

Thanks Kenrosencpa.

Any other people with thoughts on this subject?

... Altan

Here is a plot of some real data originally collected by danielo from a H79 projector. Over the years, on this forum, others have reported data with a similar trend:

http://gallery.avsforum.com/data/501/H79Lamp.gif