I need some advice. I tried the raynox 2000A on my tamron 18-250 but there was a lot of vignetting. All shots were taken at f 5.6 and iso 1600.

Has anybody tried the tamron with the raynox 2000A before? Do you have the same problem?

After I left, it struck me that trying only at f5.6 may be the cause of the problem. Any advice?