So there you are: Your company is developing a product that will incorporate an optical system which must be a custom design. And you are responsible for the optics. Assuming that you have a reasonable knowledge of geometrical optics and access to an optical software program, the question is: When do you need a professional lens designer, and when can you do it yourself? If all you want to do is analyze a system's performance, all you need is a modest amount of knowledge and a good, competent software program. There are only a few situations where some unusual consideration of modulation transfer function, diffraction theory or some other bear trap will trip you up. The answer here to the question, "Can I do it myself?" is an almost unqualified, "Yes, indeed, you can!" But if we're talking lens design, the story may be different.