Anand,

I've used 20-25% duty cycle. In the application I mentioned, my card was powered by the PDA. I've never found a capacitor was necessary but most of my transmitter apps were RF which takes less power. I prefer BR type batteries as they maintain their charge better than most other types. Panasonic has some discharge curves comparing BR to CR. A Google search on "Panasonic BR" will likely find them.

I understood that the receiver was in the camera. I should have been more clear that I was generalizing. Still, it will help if you can find out (from the manufacturer?) what wavelength IR the receiver is designed for. Since it is intended for outdoor use, it is likely that they've used a narrow bandwidth receiver.

This might be helpful - although I think its points have been covered here by me and Bruce.

http://davehouston.org/ir-rf_fundamentals.htm