There is an endless debate about filters, but try this:
Make detailed comparisons with and without the filter. Under normal circumstances the photos should be identical, and if you can't tell them apart, don't worry about image degradation. If the filtered photos are worse, don't use the filter.
In extreme flare situations, assuming a physically safe environment, I'd remove even a multi-coated filter. Otherwise, I do use filters for lens protection, because I can't detect degradation from using them.
Paul
|