Originally posted by MitchellScott 
I just purchased a DA 50-200mm lens from here, and am loving it! I'm about to buy the M 1.7 50mm off of here too. It doesn't matter if there's a scratch on it and it's not affecting the IQ right? Thanks for all your advice guys!
Scratches usually look really bad, but don't affect the images that much. A scratch on the rear element seems to be worse than on the front, if only because the rear element is smaller - a scratch the same size affects a larger percentage of the area.
It will affect value and ease of resale. I put up this lens for sale in the marketplace at the same time as two other M50/1.7s:
The other two were $50 and sold right away. This one was $30 and did not sell. I do not think the chip degrades image quality at all, let alone 40%. As long as you don't intend to sell, this doesn't matter.
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