TIFF is cross-platform. It's also loss-less. And, it it goes through professional RIPs quickly and painlessly when using the image in print. It also supports many channels. It's a great format al around. .bmp, though viewable on most Macs, is really a Windows specific format, and it doesn't play as nicely as TIFF. I don't know if .bmp is lossy or not, I don't think it is -- not sure, but TIFF is still a better format for the compatibility with OS's and print shops. .psd is Photoshop format. It's great for using in photoshop on platforms with photoshop, but that's about it . It's great in that it supports layers; but for professional printing, it still needs to be converted to TIFF. Most pro designers keep a working copy in .psd format, and a copy to present in TIFF or EPS. It's a pain, and hopefully psd (or other comparable substitute) will become standard and make designers' lives easier, but until then, we're stuck with the TIFF.