Hoya Blue Enhancer (Intensifier) Filter

This Blue Enhancer (Intensifier) Filter from Hoya is designed to enhance blue colors of the spectrum. When a circular polarizing filter alone cannot enhance enough of the blue colors, because of a cloudy sky, combine the Blue Enhancer and a Circular Polarizing filter together and it will intensify the colors and increase the contrast of the image.

The Blue Enhancing filter has a filter factor of 2.5, so you should increase your exposure by 1 and 1/3 of a stop to compensate. Transmission of light passes easier through the filter, because of a single type of coating, which has been placed on both sides of the glass; reducing reflections off the surface of the filter. The ring is made of aluminum adding strength and protection to the lens while is it screwed on.