Here's a quote from a debunking site specifically talking about this picture.
"Film is not a perfect recorder and in the case where an object is so bright white, it will saturate and bleed over into adjacent parts of the emulsion. If you look at the very edge of the cross-hair where it hits the antenna on the rover you will see that it is slightly darker and does slightly cut into the image of the antenna despite its saturation. You need to look at the original image, however."
To even further prove this, look at the photograph very carefully and tell me how many cross-hairs you see. There should be 12 (four rows of three) but you can really only make out five and partials of a few others. Some have entirely disappeared due to color saturation from the bright white.