Peak moment, You Connect member Willem Melssen, Canon EOS 50D
Backgrounds become less important, because they will usually be out-of-focus. That’s because depth-of-field will be at a minimum. Depth-of-field is the area of the image that appears to be in focus. When shooting landscapes with a wide-angle focal length (28mm, for example), depth-of-field can extend from a few metres in front of the camera to infinity. However, with close-up photography, depth-of-field is very narrow, sometimes only a few millimetres wide.
Using Aperture Priority AE (Av) shooting mode and setting a small lens aperture (such as f/16 or f/22) will increase the depth-of-field a little, but means that you will have to set a slow shutter speed increasing the risk of blur from camera shake. If you do need a short exposure, then raise the ISO to compensate.
With a very limited depth-of-field, accurate focusing is critical. If possible, switch off autofocusing and focus manually. This lets you choose the point-of-focus, rather than leaving it to the camera.