Many spotting-scopes have eyepieces that can be adjusted to add zoom. In addition to magnifying the image, changing the zoom will alter the focus and brightness of the image, as well as remove vignetting. The table above shows how zoom affects images taken at two different ISO settings, with focus corrected.It should also be noted that too much zoom can cause visual aberrations around the edges of the image, depending on the performance of the eyepiece.All pictures were taken at dusk, using a Canon EOS Rebel T3 mounted on a 20-60x80mm spotting scope.