You may not need to adjust quality settings for an entire scene. Adjusting settings on a per-object basis is often more efficient and has less of an impact on rendering speed.
For more information on aliasing artifacts and strategies on how to fix them, see Anti-aliasing and flicker.
The options in the Presets drop-down list and the Edge Anti-Aliasing Quality drop-down list drive each other; when you change one, the other changes, and values for the Anti-aliasing subsections are automatically filled in. You can fine tune any of these settings.
Do one of the following:
The options in the Presets drop-down list drive values for other settings in the Quality section of the Render Settings window. You can fine tune any of these settings.
Do one of the following: