To bad this is 3900k

[newby]

Would this have been a good light if not for the 3900k?

http://cgi.ebay.ca/400-Metal-Halide-...QQcmdZViewItem

[Guy Grotke]

For projection we need to have a light source that "looks" as small as possible, because the fresnels need to focus all the light to get it through a small diameter projection lens. You can use a spherical reflector, because it does not increase the effective diameter of the light source.

Even with fresnels to focus it down, this lamp would give you a very wide circle of light at the projection lens, so most of that light would not get through the lens.

There is another possible reflector type that could work: If you found a perfect parabolic reflector, with the arc at the focal point, then it would send rays out mostly in parallel. You could use just a field fresnel to focus those parallel rays down to a spot at the center of the projection lens. You would lose most of the light coming directly from the arc, but all of the reflected light would get there.