I agree with the OP about how IDL greatly adds to the realism of a render but I think you'll always have to use postwork to get anywhere close to photo realism. I'm experimenting with using Photoshop's RAW settings to reduce the 3D "clearness" and flatten the render a bit. I also find it good to add grain, at least to the shadow parts.

IDL is addictive. In some ways I hate it. Everytime you get greatly increased render speed you get a new toy to slow it down ;)

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