In the info on the used product it says for the D750 " ... Sale of goods in mint condition, which may have minor defects in appearance, functionality ... may be present. " Is it possible to name the small defect? By "in the optics" is a defect in the optical path of rays something wrong. If so, does it affect the image, i.e. the shot, in any way? Or is it only noticeable in the viewfinder and/or on the display? Can you be a little more specific? Is the warranty the same as for a new product? Thank you