Why does using only one color with different shades (like all blues) make you really notice how bumpy or smooth things are in a photo?

Using only one color with different shades, known as a monochromatic palette, makes the bumpiness or smoothness of objects in a photo more noticeable because it eliminates hue (the pure color itself, like red or blue) as a primary visual cue. Our visual system then heavily relies on value, also called luminance, which is the lightness or darkness of that single color. The perception of three-dimensional form, including texture, is fundamentally based on how light interacts with a surface, ....