Hi I have been photographing weddings for a while but had a long break, just got back recently, upgraded my flashgun from 430ex to 600rt and I notice that sometimes the photos are underexposed. It is very annoying as I don't understand it at all! I use ETTL (direct flash or 45º or with gary fong lightsphere), I use same exposure usually, 800ISO, 60 5.6. Sometimes it might be because of black or white clothing but I do use spot metering. I don't know how to overcome it, thanks god for lightroom so I go through all the photos, correctng exposure in some. The photographers I work with use Nikon and all their photos are perfectly exposed, they use their flash on Automatic mode and it gives them perfect exposure each time. Anyone had a simillar problem with Canon flashgun or have an idea how to solve this? I tried shooting with flash on Manual, but it is not always possible as when everything is changing quickly and I move from long shot to wide, from close up to group portrait in seconds, I can't adjust the flash too often. I attach 2 photos I shot one after the other, one perfectly exposed, the other 7 sec later (enough time for flash to recycle) much too dark. Will appreciate any feedback Thank you very much!