White elements on POV image

When the number of digits were set to four, white elements were disappeared but in some place surface is lost its smoothness. I checked the image without light, it appears as I expected. I hope the surface non-smoothness due to the light reflaction or refraction.

The number of digits of nodes four or less than four in POV file could be a best use for good image view.

In my case the least number of digits is four.