Ooops, obviously I didn't read the start of thread. It's not a lightbox, it's a softbox ;) Sorry (thumping head on nearest wall)! Anyway, my advice still holds - the tubes sold for labs & printing bureaus where they need some daylight (5500K) balanced tubes, should work for the softbox application as well. I think they are called HDT tubes? I am not sure :( See the url. Frantisek