Cheers Guys!! Thanks for the comments.

What I wanted to do was see what adding lights to a HDR image would do

I created the diamonds using a poly cube and just used a poly plane for the floor

To position them I set the diamonds to active rigids and the floor to passive created a gravity field then played back the animation to get then into a "random" position on the floor.

I then used a white mental ray dielectric material for the diamonds, adjusting the lor in image (to about 2.6)

The floor was then just the default lambert

I added a spotlight as the Key light, and a directional light as the fill light, (I was aiming to use the HDR image as the back light and to cast some colour onto the diamonds) and adjusted the levels with a few test renders with the following settings (but at a low resolution).

Oh I lowered the colour gain on the HDR image to offset the spot and directional light, just so the HDR would cast its colours

For the rendering I first added a HDR image, dissabling the default light, I set the reflections/refractions to 10 and enabled raytracing, enabled caustics, with accuracy to 60, enabled final gather and set the rays to 500
(i played about with the min/max radius but it didn't make that much difference)


That was it really, just a little tweeking of the levels in photoshop and that was it.

Hope it helps you out!!

Cheers