Originally Posted by DeanCapture

If your lens is a variable aperture lens, and depending on what aperture your using, you may notice some of the pics are lighter and some are darker as you zoom thruout the focal length of the lens. I use constant aperture lenses and do not have those kinds of problems. All of my lenses are F2.8 lenses thruout the zoom of the lens. You may also notice problems like these when using aftermarket lenses especially cheap ones. By aftermarket I mean lenses that are not made by Nikon, Canon or a some of the other top glass/lens makers.