Dear all, Somebody has asked me to take indoor residential photographs of his work as a professional plasterer, to happen in about two weeks. While I think of myself as an intermediate-to-almost-advanced photography enthusiast, I have no substantial experience with flash photography if that is what I may have to use. I have a Canon 5D Mark 3 and a 550EX flash (are they even compatible? I won the flash more than ten years ago but never got round to study flash photography in appropriate depth, apart from a few occasions when I tried the flash unit more for fun than anything else) coupled with a Sto-Fen diffuser if needed. I will be using either a 16-35 f2.8 L or the newer f4 L IS version I am swapping it for. While I study the whole matter in detail from here to when I take the photographs, is there anything at all that any of you feels to tell me, anything that comes to mind that I should know about? It may be that I am able to use natural light but the question above any useful information still stands of course, regardless of the use of flash or not. Thank you to anybody pitching in to share their views.