The Hoya HD Nano Mk II CIR-PL filter lets through around 2/3 to a full stop of light, which corresponds to a light loss of around 1 to 1.5 EV. It is characterised by very high light transmission and, according to tests, allows around 25 % more light through than many standard polarising filters, which corresponds to around half an f-stop more brightness.

For comparison: The B+W circular polarising filter T-Pro HTC is also known for its high quality and low light absorption, but exact values for light loss are not explicitly stated in the available sources. In general, B+W T-Pro HTC filters are designed for very low light loss and high transparency, comparable to high-quality Hoya filters.

To summarise, the Hoya HD Nano Mk II CIR-PL filter consumes very little light and is one of the filters with particularly high light transmission. The B+W T-Pro HTC polarising filter is also very light-transmitting, but exact comparative values are lacking. Both filters are among the top products with minimal light loss, whereby the Hoya filter is explicitly stated to have a loss of approx. 2/3 to 1 f-stop.