I have the opportunity to purchase a used 80-200 AF 2.8 ED lens in good condition. I took some sample images at the store. The pictures were taken at f2.8 with a flash. To get the depth of field "normal", what should I have set the aperture at? Also, the skin tones are different than my kit lens, is this normal. Here is a re-sampled crop. Does it look okay? Also, what would a fair price be. Thanks.