When using Maya and Mental ray to create fisheye formatted images, Andrew Hazelden noticed that renders were coming back with artifacts for shots that had an image plane attached to the camera for checking safes. Finding the image planes to be at fault when using custom mental ray lens shaders, Andrew was able to solve the problem by using a Maya Hypershade Network that can be used to overlay alignment grids, text, captions or test patterns over a metal ray render.

I would like to present a camera set up that can be used to render alignment grids, test patterns, or text captions over images in the Maya render view

Not only does Andrew show us how to create screen-space image overlays for mental ray, but he also walks us through his problem solving process providing attempts, a workflow summary, and an example scene as well. Check out the post for Creating Screen-Space Image Overlays in Maya with Mental Ray here.