Mild broadband filters allow the widest range of wavelengths to pass through them. Compare one of these to other types of deep sky filters by holding it up to a lamp; you will see that it looks "light" in comparison. These LPRs are referred to as mild filters because they have the least effect on deep sky objects. There is a contrast boost; some light pollution is being stopped, but the increase is less than in other LPR types. Lumicon's Deep Sky filter is a mild filter, as is Orion's Skyglow model.
Why would anybody want to buy the least-effective type of LPR filter? One reason is that broadband filters can be used in picture taking. Although the narrower filters are sometimes used in deep sky photography, they are so dense that they require long exposures even on bright objects. Another reason to choose a wideband filter is because, in the opinion of some observers, they can improve views of galaxies and star clusters. It is said that these filters darken the sky background just enough to make galaxies look better without dimming their stars too much. Personally, I have never seen much—if any—improvement in galaxies or star clusters with one of these filters.
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