Hi everyone. I am wondering if anyone can streer me in the right direction here. I run, as a sideline, a licensed private investigation service. I undertake quite a lot of covert photography and have bought a new Canon 400D. I would like to know some optimum settings, which I know will be a bit hit and miss, because the light will vary on every shot, but I want to at least have a starting point. I usually have a photgrapher do this for me, so Im struggling a little with clear crisp shots at present. My main photos will be of subjects usually within 30 - 40 feet of my camera, usually in the street or outside somewhere. These targets will usually be moving (ie) walking pace etc I need to take pictures, without flash of said moving person sometimes in twilight and more often than not during daylight hours. What F numbers should I be using and ISO? I have tried on one subject but end up with a blurred image, so obviously my settings arent quite ball park. I normally use a 70-210ef lense for this purpose. Any ideas?