RWR wrote:
Any glass (or resin) on your lens that was not included in the optical formula is bound to have an effect of some sort on the image. However, with a quality, perfectly flat filter the effect will be negligible. After all, filters have been used routinely with film, particularly black and white, since about day one of photography and countless millions of photographs have been made with them with scarcely a mention of image quality degradation. It really is pretty much a moot point.
Do old film era filters tend to shift color over time? I've got an old skylight / UV filter that seems to create a bit of yellow compared to not having the filter on.