I've been doing my homework around the forums in preperation to do my first build. . .

I'm a little confused when it comes to reflectors. I plan on using the S400DD buld so according to the conventional wisdom around the forums, the Ikea napkin holder would be appropriate. For some reason I thought a perfect hemisphere would be better though. . . Why wouldn't it be better to use a mixing bowl or some other stainless sphere?

Any input would be great.

Thanks,
Chris

The reflector does need to be a spherical section, but it does not need to be a full hemisphere.

The reflector needs to be large enough to cover the backside of the arc which will hit the fresnel, and go on to hit the triplet. This is an arc of les than 45 degrees. The Ikea napkin holder covers more than this amount, making it appropriate for use.

A picture is worth...

SupraGuy: Understood that the reflector does not need to be a full hemisphere but are there any issues if some of us who are currently using these types of reflectors in our projectors, meaning would we get a better image if the reflector was just big enough only for the rear of the Ushio?
sim

If you still have the amount of hemisphere greater then or equal to the amound needed for the arc to refect on the usable part of the fresnel it should not matter.

if anything you stop more light from leaking out the exhaust fan holes with a bigger reflector, which is a plus!

A larger reflective surface will not help yor projection any, but it won't hinder it, either.

It will help block stray light to the back of hte projector, which is a good thing, though it will also concentrate more heat at the lamp, which may or may not matter.

Basically, I'd say it's fine.

Thanks guys. Very helpful.

Best,
Chris