Ah, there is a big difference - but only on certain types of render. As Incarnadine says, detail, especially on distant objects, can be entirely missing on standard render, whilst present on fine art. The image I included doesn't show it too well because the proc texture is blurred anyway, but it gives an idea. When I'm spot-rendering in the last stages of a pic I always use fine art or premium32+ because otherwise I tend to miss stuff. And reflections don't come out well on standard, either. I normally use premium 64 for renders unless the time is prohibitive, when I use fine art 16 or something. I've yet to find a difference between 64 & 256 rays per pixel however... ;)