Does this affect image quality?

Please help!!!!


I just bought an used Sigma 18-35 lens . Everything is fine except this small scratch or nick at the rear element and me being an amateur, I am unsure about its impact on the image quality.

Can anyone here help looking at this picture and comment if that would affect image quality?

https://flic.kr/ps/bUV​Z4

I'm not an expert, but I don't believe you'll see it in your normal shooting. My Olympus 25mm f1.8 has a decent size smudge that I've yet to clean off and it has not once shown up in any photo. If you shot the lens at minimum aperture (f16 or f22 depending on the lens) directly up at a clear blue sky you MIGHT not something.

This photo was shot with the 25mm (that has a strong smudge line halfway across the front element) at f4 (f8 35mm equivalent); very low contrast neutral-toned subject that would be perfect condition for something like that to show up, but nothing!

IMAGE LINK: https://flic.kr/p/28pb​V24

A lens with a mark on the front element is not likely show any loss of quality because the front is so far away from the focal plane. The rear element being closer to the focal plane might show some effect on IQ. The minimum aperture and blue sky test might show something. I'd also just do some other tests with details in the pic. Maybe some kind of repeating pattern on a flat surface parallel to the sensor, again with the lens stopped down.

I will do a blue sky test and a repeated pattern as you suggested.

You have to do more than that to affect IQ. I shot a Nikon 24-70 with a wrecked front element and it just made a smudge at f/16

IMAGE LINK: https://flic.kr/p/c98F​to

IMAGE LINK: https://flic.kr/p/c98F​nL

Thanks. How does it impact the resale value of a lens?

I would say at least 20% off for a rear element scratch... depending on size and location. over to the edge is better.. dead center could easily make it 25% less or more.