A lens design or optical treatment that reduces diffraction fringes and softens the edges around bright points of light in an image. By gradually decreasing light transmission toward the edges of the aperture, apodization improves the quality of out-of-focus areas (bokeh) and creates smoother tonal transitions. This feature is especially valued in portrait and low-light photography, where pleasing background blur and reduced halo effects around highlights enhance the overall aesthetic and image quality.