I recently bought this lens from KEH in EX condition. It is in that condition w/ one exception. There is a bubble or something on the the rear of the front element (or the front of the rear element) that is rather obvious. I can return it for full refund at this point. The only things that concern me are image effects and resale value. Can anyone w/ experience tell me whether this will ever affect the image in any way? I believe it will definitely affect resale value. Can anyone give an opinion on that? I use these lenses, but I also resell them from time to time and do not want to take too big a hit. Pictures are attached. The bubble is more obvious than the photos make it appear. It is right in the center: in the first image it's dark, in the second it's light hued. Thanks.