Here I have the 580EX mounted on a FLEX TT5 on camera set at +1 FEC (MAIN). The 430EX II mounted on a FLEX TT5 with wide angle diffuser on camera (L) to illuminate the background FEC -3. The 550EX mounted on a FLEX TT5 with homemade snoot of three sheets of printer paper rolled around the flash head and held in place with rubberbands, handheld at -1.5 FEC (FILL). Look closely at the two sample images and see if you can tell where the handheld flash was held in relationship to the subject. Also compare these images to the images in the Two Strobe Setup. I think you will agree that adding a third strobe to the setup for FILL FLASH does add more depth to the image.