While Carolly is 100% correct, I must admit I mostly save my stuff as 100% JPEGs, as I just do so many test renders that I'd fill up the drives otherwise. However, I plan on reducing the image by at least 25% for a throw away, and 100% for anything serious. I find it a lot easier to smudge out the Poser bad elbows and knees on a double size version too.