I have an opportunity to pick up a slightly dirty light tent for $20. It's fairly large, I would imagine around 20" x 20" foot print with a large opening, side panels and a curving rear curtain. It's held up with criss-crossing metal rails and kept open with a supporting rail on the bottom. My concern is that it is visibly dirty. The material is no longer perfectly white but somewhat gray, dusty with some spots. So, will that cause uneven lighting or strange shadows/spots in my negatives? Thanks... Otherwise, $20 seems like cheap enough for a largish tent.