The 27mm #25 Light Red Filter from Heliopan is designed to build strong contrast in black and white photography. The filter will make skies look more dramatic and give a tonal difference between foliage and flowers. Infrared images can also be enhanced by the filter, giving a moonlight effect. The colors blue and green are completely absorbed, which will make them darker and increasingly show more contrast. This filter will also cut and remove haze from a black and white image. Exposures should be increased by 3 stops, because of the 8x filter factor.
The ring is made from brass, which will prevent it from getting stuck on the front thread of a lens because of the pliable nature of the metal. The brass ring also has front threads, so filter stacking is possible. Schott glass is a high grade of glass that is used for all Heliopan filters.