Just bought a used Sigma 10-20 f4-5.6 EX DC HSM lens. It's in pretty good nick but the front lens looks to be slightly greasy. Tries a Lenspen to no avail and also some Optical Wonder fluid. Still looks a bit grubby. Any ideas for cleaning the lens properly? I have had loads of lenses and never had a problem before.
Thanks
Brian
Thanks
Brian