Depends on what res you want and what kinda of computer you have these setting can really chew up rendering time and resources on you computer so use them at your own risk!!
Before I Go futher I will disply my machine specs. You can kinda of get an idea from there.
- AMD 2000+ (1.7ghz) processor 32bit
- 1+gig of DDR Ram
If i am just going for a standard wallie i set it up like so
Size: 1024x768 (I am slowly going to 1600x1200)
Quility: You can use 2000, but if you really want a nice image set it to 4500 to 5000
(You have to type that in BTW)
Filter Radius: set to 1 you can if you choose set it to 2 but i do not suggest going higher. Setting it to one will help get rid of any graininess you have. Any higher than 2 you will loose finner detail and bump the render time way up. It will smooth out the graininess but at a much higher cost to the final image.
Oversample: I never really adjust this that much i may go up to 3 but i have yet to see any real drastic improvment from the default setting of 2. It will however chew up alotmore ram if you set it above 2.
The buffer depth is up to you... Higher buffer the more ram it is going to chew up in rendering, but it will render faster. I usly leave mine at 32bit and i don't set the limit.
Ram used - setting it to 1024x768 w/ q = 2000 fr = 1 and os = 2 uses 48mb on a basic (2 triangle w/ less than 6 variations) time: 15mins
Ram used - setting it to 1600x1200 w/ q = 5000 fr = 2 and os = 2 uses 117mb on a basic (2 triangle w/ less than 6 variations) time: 30mins to an hour+
If you want to render a print size for DA than you need to use 3200x2400(you can go bigger but you have to use flam3) with q = 5000 fr=2 amd os=2 it is going to use 450+mb ram and it is going to take at least 4 hour to render.