Would this have been a good light if not for the 3900k?
http://cgi.ebay.ca/400-Metal-Halide...742922666QQcategoryZ42225QQrdZ1QQcmdZViewItem
http://cgi.ebay.ca/400-Metal-Halide...742922666QQcategoryZ42225QQrdZ1QQcmdZViewItem
reflectors
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.
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.
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