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Well first off, some narrowband filters are well down the visual range of the human eye, Ha and Sii specifically, in the deep red band. Oiii and a few others are within the visual range. Secondly, narrowband filters, as used in imaging, have steep cutoffs, so only the particular frequency is allowed to pass. When used in imaging long capture times are required to gather the passed through signal, and the human eye lacks the ability to take time exposures, so your limited to what you can see at the moment, unless your doing EAA (Electronically Assisted Astronomy, which is a form of imaging that uses frame stacking in real time to build an image). There are some filters that are primarily light pollution filters, that block the usual wavelengths of some street lights, but as more and more councils move to be had spectrum LED lighting these filters are less effective. However, selective broader band filters can be useful for visual use in light polluted skies.
The filters you choose need careful selection for your particular area and situation. Research is key.
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