I occasionally shoot hummingbirds in our backyard and normally set up about 8 to 10 feet from the feeders. The hummers don't seem to mind my presence as long as I don't move around too much. I usually use a 300mm lens on a DX camera and get what I consider good framing - not quite frame-filling but near enough. I have shot both natural light and flash. When using flash, be sure to disable any pre-flash feature. The hummers are fast enough to move nearly out of the frame between the pre-flash and the main flash. Once they realize that the flash won't hurt them they tend to settle down a bit - they still move, but not as far. The direction of the light will have a significant impact on the colors that show up. When the light is just right you will get bright, vibrant colors from certain parts of their feathers. When the light is not quite right you can get very muted colors. Unfortunately, I have not done this often enough to remember what lighting worked for me and what didn't.