Oh dear, l remember an old Math teacher telling me, "If you can't avoid being stupid, do at least try to conceal it" But anyway l am starting to see the idea. Steve's comment about not concentrating ones attention on the lights in fstops, both Jeff and steve have me understanding that the fill light metered at f4 is only that bright if left on its own but combined with the key light and camera settings the fill light metered at f4 losses its brightness. I hope that makes sense. I can feel the presence of my Math teacher shaking his head in frustration..