I have been experimenting using a piece of white tissue as a homemade diffuser to soften the light of direct flash from a flashgun. I knew the operating range of the flash would be reduced, however, I tested the flash with no tissue on a subject 20 feet away - the OK light on the flash lit up to advise me that there was enough light for a good exposure. When I tried it with the tissue over the flash, I had to move to 3 feet for the OK light to illuminate! I didn't think it would affect it that much! I am using a Guide No 92 flash with TTL metering. Without tissue, using bounce flash off a white ceiling there is also no OK light, but photos I took last week were fine. Anyone have thoughts on this one? Would there be enough light using the tissue at a decent range or is the OK light correct?