Problem with the porcelain/plastic bulb holders is that they have no reflector (the painted white backing in a fluorescent troffer does a lot), lens, or diffuser and they are jammed up against the ceiling (often unpainted drywall or just framing in workshops, garages, basements, etc). I have upgraded several porcelain holders to a basic fixture with a reflector and diffuser, and it makes way more light from the same bulbs. Made me realize how lousy a bare bulb is when it's stuck right next to the ceiling. I think even if you could put a white painted board a few feet around the porcelain bulb holder it would have to help. A fixture with a diffuser or frosted globe would help even more.