The 4 x 4" #70 Dark Red Wratten 2 Gel Filter from Kodak is designed to separate tones and build extreme high contrast in black and white photographs.
The filter enhances reds, absorbs blues and greens, and is ideal for infrared photography, which blocks visible light up to 650nm. The sky becomes more dramatic and the infrared effect is intensified. The Dark Red filter is also used for color separation; combining with other primary colors to create a color image.
Kodak has made improvements over the previous line of filters, and the Wratten 2 filters feature gelatin that is more ridged and durable, with colors that are more resistant to fading and degradation. Fingerprints and smudges wipe off easier, the filters are less sensitive to humidity and create less static cling. They are also less prone to sticking to other filters or materials.