Just got a focus rail to use with my macro lens to get better close-up shots. The focus rail allows me to take several images of an object and then "stack" them in photoshop so that the entire object is in focus. Normally with a close-up shot the depth of field is so shallow that only a small part of the subject is in focus and the rest is blurred.
For this particular image (which is only my fourth attempt with using the focus rail) I shot 44 photographs of the rosebud and then used photoshop to blend them into a single image that is pretty much in focus from front to back. The rail is used to make very small adjustments in the position of the camera relative to the subject by moving it incrementally closer by tiny fractions of an inch with each turn of the adjustment screw.
Monte