With a white background you should also include:
To change the lighting of the object during a ray trace:
Other values to play with during ray tracing:
When doing a final rendering, the following will improve resolution of the image
This will give you an image 2400 by 2400 pixels. This can be used to create smaller images but with a higher resolution. After you have a 2400 by 2400 image you can convert this to a 600 dpi image using an image editor such as photoshop which will give you a 4" by 4" high quality final image.