This Chapter gives information about the optics and the sensor in an image acquisition system. Optic is the first stage of the image acquisition system and is composed by one or more lenses aiming to concentrate the light in the physical sensor obtaining an in focus image. It is one of the most expensive parts of an imaging system. In mobile cameras usually a lens is compound of a system of plastic and glass lenses stacked together, while in single lens reflex cameras (SLR) a group of several glass lenses system is employed to reduce image artifacts. In this Chapter an overview of the lenses will be discussed. Moreover, some typical artifacts will be introduced (e.g., cross talk and chromatic aberration). The sensor is the part that converts the optical image (light) to an electric signal. There are several kinds of sensors depending on the technology (CCD - Charge Coupled Device and CMOS - Complementary MetalOxideSemiconductor), on the color filter array (Bayer , Foveon, 3CCD, Panchromatic), on the transducer function (LDR - low dynamic range, WDR - wide dynamic range and HDR - high dynamic range sensors).