I have a Canon Rebel XTi and wondering what would be a good lens? I have an 18-55 Canon Macro Lens and a 75-300 Sigma Macro lens. But, I want something that I can get within an inch or two of the cora. l I want to start taking pictures through a photo box for top downs....... I am just learning the camera and typically only use the auto settings. I have a lot to learn!