Hi all, The recent camera obscura thread got me to thinking about a conventionally constructed home that we will be retrofitting with numerous green energy technologies. Without belaboring the details, one aspect of the home's design will involve using styrofoam-core shutters to block heat leakage through the windows of unused rooms, which of course will render those rooms completely dark. Now what better way would there be to provide a minimum of lighting to a room than to introduce a camera obscura in each room, which would project views of the river behind the house? Pretty fitting for a photographer's home, eh? The problem is that the light from a tiny hole (even maybe a 1 cm dia hole) is going to be quite dim. The obvious way to make this work would be with a lens, but the lens would have to be of quite long a focal length, generally about 14 or 17 ft, depending on the room. It would also need to be of a fairly large diameter. I've looked around for simple meniscus lenses, fresnel lenses, and/or parabolic mirrors that might have this sort of focal length, but the best I can find is on the order of 1m focal length (about a quarter of what I need). I suppose I could combine converging and diverging lenses, where the diverging lens is very slightly weaker than the converging one, but I'm still stumped as to where to find such beasties. Image quality isn't of paramount importance. I just want a cool projection to amuse me and those who visit our home. Any ideas? Any thoughts where I could find such lenses? Thanks!