Selecting the right lens manufacturing vendor is a multi step process. Starting with detailed production drawings, quotes and vendor reliability are evaluated. Vendors need to provide details on their testing abilities to ensure the match between your design and the product made. Depending on the type of lens and precision required in your application. In most cases you don't need all the tests listed. For many applications, a photo of a USAF target is good enough while some need the more expensive and time consuming MTF test. Testable lens elements include measured radius and thickness, surface irregularity. Completed lens assemblies have their tests including distortion, field shape, and magnification.