Dear jeff7id, the more extension tubes you add, the less light reaches the sensor. There is no degradation of image quality.
Can you please state the equipment you used? Or are you simply hypothesizing?
I've shot with 4x5's for close to 20 years. The bellows simply distance the same lens from the film plane, when extended. None of any 4x5 lenses are dedicated closeup/ macro/ micro. Yet every single one of them shoots absolutely brilliant closeup images. it's not 1:1. It's more like 25:1 (25x) magnification, especially when we were shooting for jewelery clients. Don't forget that the film is 4 inches by 5 inches large.