Mark in image from 24-105mmL Lens

[mimmt]

I have recently started noticing the mark in the top left of all my photos when shooting with this lens. I've tried to clean the lens but it seems to be in the glass. 

Could someone please explain what this is and how I can resolve the issue? 

Thanks

Karl

[ebiggs1]

A scratch on the lens is OFF (out-of-focus) and will not show in the photo. Unless you stop down to f16 or f22, but even than rarely will you see it.

A scratch on a lens can induce flare.

A scratch on the lens can also cause enough light diffraction to effect contrast and color.

A scratch itself will not show up in an image looking like a scratch.

Are you sure it is on the lens?

[mimmt]

Thank you for the reply ebiggs1. 

My first reaction was a mark on the sensor but I ruled that out testing with another lens.