Of "didymium" glass, this filter increases the color saturation of the blue spectum.
It is achieved through the selective blocking of the colors around the color being intensified.
Through this process Hoya has developed a filter that subtly increases saturation of blues and blue-greens such as sky and foliage while not giving an over-all color cast to the photograph.
The filter is most useful for photographing outdoors in noontime sun, when a circular polarizer is least effective for darkening blue sky.
Reviewed by 1 customers
I use this filer extensively during the fall for foliage shots. This filter will not add red where it is absent but will enhance existing reds and browns, adding vibrancy to a dull scene. It also works well for animals and plants that are red or brown (white tailed deer, red fox, cardinal flower). It will even bring a richer tone to a forest floor blanketed with brown leaves. I have also had good results with sunrise/sunsets as well. Christmas is another time of year when it works well, as there are many red lights and decorations, and santas suit will glow. It really is a must have filter.