Hello. I am looking for an external flash to use with my GRD for one reason only. I just want to use it for photographing book spreads for documentation. Therefore it cannot be a slave because the ricoh built-in flash would be to bright. Am I right? I woould need a flash that does swivel/tilt. Therefore I could only use the recommended SIGMA and the mentioned NIKON or the Metz 20 C-2. Or do you have other recommondations? Thanks in advance.