iff is a native Maya file type, if you are rendering for a 3rd party app then try tga or tif as they have the best quality (imho). If you need alphas then go for tga files.
Chris (formerly R@nSiD)
Twitter
When the power of love overcomes the love of power the world will truely know peace - Jimmy Hendrix
Winner SM VFX Challenge 1
3rd Place SM SteamPunk Challenge (May 2007)