When a diamond’s total depth is too low relative to the average girdle diameter, it is said that the diamond is too shallow or spread (spready).
Shallow diamonds lack depth compared to ideal cut diamonds, which is why most of the light entering does not reflect through the table but leaks out from the bottom of the stone (pavilion), sacrificing its brilliance and sparkle.
Moreover, shallow cut diamonds tend to exhibit a “fish eye effect”, which occurs when the girdle of a diamond is reflected under the table facet. This phenomenon always detracts from the beauty of the stone.