Question

Who am I? That when I am more you can see less and when I am less you can see more?

Answer 1

The answer to the riddle is DARKNESS.

For we see less when it is more.
And we see more when it is less.

It matches both the conditions and so darkness is the answer.

Answer 2

Answer is darkness or dimness. Hope it helps and pls mark as the best answer. :-)