Does carpet block light travelling through it like from glowstone? If so what is the reduced light level from each carpet?
According to the wiki "Carpet is an opaque block, however, it does not decrease light going through it."
In fact, the wiki even recommends placing light under carpets: "Carpet allows light to pass through it. [...] Jack-o-lanterns are often used as a hidden light source that is considered both useful and visually appealing."
(image taken from the wiki)