Is this a good reflector?

[voovoov]

I came by this bowl at amazon while I am searching for a good reflector. It appears that size is ok, my question is whether it can be used as a reflector.
Here is the link:
http://www.amazon.com/exec/obidos/tg...ance&s=kitchen

Thanks

[unit24]

Looking at that image, I'd have to say no. It is not a true hemispherical / ellipsoidal shape. There is that depression on the bottom that would cause problems with the light being reflected.

I'd pass on this.

This or this may be a better source.

[voovoov]

Thanks unit24.
They are looling very good. Has anybody tried them?
Another question. I am using 15" LCD and a220mm BF, which size of the reflector is good? how about the 3.25" one?

[mdorani]

isnt it possible to cut a softdrink can in half and use that as a reflector?

[Guy Grotke]

Yes, that is generally called a "beer can reflector". It will reflect some additional light toward the LCD. But it will also give you a blurry image.

Projection needs an even cone of light going through all parts of the LCD, and then getting to the lens. There are two ways of doing this:

1) A light source that is the size of the entire LCD with even illumination over the entire surface, with a field fresnel to make the light converge to enter the projection lens. (The field fresnel can be on either side of the LCD.)

2) A point source lamp that sends a diverging cone of light to a condensor fresnel. There it is refracted to a parallel or converging cone and sent toward the LCD. Either before or after the LCD, a field fresnel may be used to converge the light even more so it enters the projection lens.

Using a beer can reflector makes it look like the light source is bigger, so it doesn't get refracted into a nice even beam. A good spherical reflector with the lamp at its center of curvature sends all the reflected light back through the lamp arc. So it still looks like a small light source. Result is a better picture.

There are lots of things that have the right shape and are reflective. I have read that people are using one of Ikea's napkin holders too.

[unit24]

Guy,

Do either of those sources have what would be useful?

[Squalish]

Voovoov yes, it will work, the internal bowl is a perfect polished spherical reflector. One of the better choices out there.

Several on Lumenlabs have used them with success, pics:
http://mywebpage.netscape.com/d00ks%20pwner/0421.jpg
http://mywebpage.netscape.com/d00ks%20pwner/0419.jpg

Re the hemispherical molds: They've been tried, the inside is matte, needs several hours of polishing to work.

[Guy Grotke]

>matte surface

Not all of them are matte (actually brushed). I got one from:

http://www.dr.ca/e_pcercle.html
(See the Stainless steel half sphere moulds section.)

It had a mirror finish. No polishing necessary. They have many different sizes too, so you can get one to fit your lamp once you figure out what size you need.

The only problem I had was that the minimum international shipping cost was more than the cost of the mold I bought! They did say I could have had three or four shipped for the same shipping cost, so it would pay to make a small group buy.

[sid58ney]

I am looking for reflector for my lamp long time already until I found your tread but I have one question about the size of reflector I should to purchase, there is so many different size of bowl and I am wondering which size is better for my lamp

the lamp I use is ushio 250 w bulb

Thank you

[juice_e]

ya, same here, i have a 400W Ushio Conversion lamp, whats the best size bowl