I keep hearing that a rear element scratch is much more horrific than a front element scratch. This sounds logical but does anybody have any first hand accounts about rear element scratches that they could share? From what I can find front element damage usually results in flare and loss of contrast/sharpness, if any impact at all. Rear element problems seem to get very vague. 50/50 opinions on running for your life or using it with no noticeable effect.