The gamma correction feature is located in one of the little triangles next to the render and camera tools - It's the lower-most one, right next to and below the trackball. I'm also not sure which versions of Bryce have this option.. I know that 4.01 and 4.1 on Win/Mac do, but does 4.0? I dunno. The gamma correction option attempts to correct for the difference between Mac/PC monitors and "the real world". IMO, it's pretty useless: it has no controls to adjust the target and source gamma, and you can get much better results using an image editor like photoshop. I'd say try rendering the image once with gamma correction on and once with it off, see if you can tell the difference, and make sure to check dark images on both Windoze and Mac boxes, because they'll look different. cheers