Ren mentioned PSFs (point spread functions) in lecture. The PSF is a system's "impulse response" to a point light source. If you're familiar with MTFs (modulation transfer function) found in the spec sheets of some cameras and lenses, you will know that it deals with the spatial frequency domain of the image. But PSFs deal directly with the spatial domain, so it's very easy to visualize their effect on images, as shown here.
Ren mentioned PSFs (point spread functions) in lecture. The PSF is a system's "impulse response" to a point light source. If you're familiar with MTFs (modulation transfer function) found in the spec sheets of some cameras and lenses, you will know that it deals with the spatial frequency domain of the image. But PSFs deal directly with the spatial domain, so it's very easy to visualize their effect on images, as shown here.