I assume the obvious answer is: As close as possible.
I am using a small reflector taken out of a overheat projector and a 150 hqi double ended. I once placed the bulb glass housing touching the outer edges of the reflector. This seems like a good position but I was worried it would overheat the reflector and crack it.
I am using a small reflector taken out of a overheat projector and a 150 hqi double ended. I once placed the bulb glass housing touching the outer edges of the reflector. This seems like a good position but I was worried it would overheat the reflector and crack it.
best reflector distance
If it came from an OHP, then it is probably a spherical reflector. The best place for the lamp arc is at the center of curvature. (If the reflector was a full sphere, then the center of the arc would be at the center of the sphere.)
You can find the center of curvature by measuring: The center is the same distance from all points on the reflector surface.
You can also find it with a small flashlight bulb driven by a low voltage. Lower the voltage until it is not too bright to look at directly. Then move it out along the central axis of the reflector, until the reflection is right behind the filament. You should be able to move your head around and still see the reflection behind the filament. That happens when the filament is at the exact center. The middle of your lamp arc should go there.
If it came from an OHP, then it is probably a spherical reflector. The best place for the lamp arc is at the center of curvature. (If the reflector was a full sphere, then the center of the arc would be at the center of the sphere.)
You can find the center of curvature by measuring: The center is the same distance from all points on the reflector surface.
You can also find it with a small flashlight bulb driven by a low voltage. Lower the voltage until it is not too bright to look at directly. Then move it out along the central axis of the reflector, until the reflection is right behind the filament. You should be able to move your head around and still see the reflection behind the filament. That happens when the filament is at the exact center. The middle of your lamp arc should go there.
- Status
- Not open for further replies.