The Breakthrough Photography Light Pollution Filter is a spectral-cut filter using special coatings to cut out spectral regions that are typically polluted by light from populated areas during night shots.
I’ve just received an 82mm sample for evaluation which I plan to shoot it in late February / early March in the Death Valley area [I have an opening for one or two people for a photo tour at that time].
The Breakthrough Photography Light Pollution Filter cuts out the orangish haze typical of polluted night skies and was designed in collaboration with a NASA scientist from the International Space Station.
The filter is a bandpass filter that uses coatings, so it shifts color outside the central area when used with wide-angle lenses. At 21mm, the shift is very strong (magenta into the outer zones), so it is best used with longer focal lengths.
I’m looking forward to seeing if the filter will clean up the background haze in skies like this for astrophotography, though regrettably a 95mm version is not yet available (the Otus 28/1.4 takes 95mm filters). But plenty of lenses take 82mm filters and the Breakthrough Photography step-up rings make 82mm good for 67mm and 77mm filter-size lenses.