In this tutorial, we present a guide to the multidisciplinary science of building the eyes of a vision system. CMOS image sensors have been instrumental in lowering the barrier for embedding vision into systems. Their high degree of integration allows photons to be converted into bits with minimal support circuitry. Simple protocols and interfaces mean that companies can design camera-based systems with comparatively little specialist expertise. To produce high-quality output, the image sensor and optics must be carefully co-optimized to fit the application. To assist with component selection and help avoid common pitfalls, we will describe the key parameters and provide a practical guide to selecting both sensor and optics for a camera. We’ll also provide an introduction to other hardware considerations and to correcting optical aberrations in the image processing pipeline.