Rainbow Research Optics Offers complete optical data design. They provide the following charts to help you determine your specific needs. Click on any of the links to go directly to each chart. The following are the different charts offered on their website: Lens Terminology, Focal Length Formulas for Singlet Lenses & Mirrors, Effective Focal Length of Two Thin Lenses, F-Number (F/#), Numerical Aperture (N/A), Sagitta (Sag), Using Wedged Windows, Selecting a Prism, and Waveplates. For more information on any of Rainbow Research Optics services visit www.rainbowoptics.com.