When the same images are presented, they do not necessarily lead to the same perceptual experience. Depending on the viewing condition or observing individual, the same color can appear different, and the different orientations can look identical. Psychophysics tries to quantify such subjective visual experiences and explore the relationships between the physical properties of the visual stimuli and the accompanying percept of them. In this talk, I introduce the basic classical psychophysical methods with examples using such methods.