Many thanks for starting this forum, Sean. I hope it will become a great source of help and information on macro photography.

To tag a quick question to what is essentially a lame attempt to be the first person to post on the forum : is there any way to easily measure the amount of light lost to a diffuser or softbox attached to a flash and come up with a revised GN for doing manual flash photography? I can only think of testing as the alternative but am wondering if there is any other way.