A Leitz Oben yellow vintage camera lens filter is a type of optical filter that was made by the German company Leitz in the mid-20th century. It was designed to be used with black and white film photography and helps to enhance contrast and reduce haze by blocking certain wavelengths of light. The term "Oben" refers to the fact that the filter is designed to be mounted on the top (or "oben" in German) of a camera lens. The yellow color of the filter helps to increase contrast in black and white photos, especially when shooting outdoor scenes with blue skies and white clouds. The filter also blocks some UV light, which can help reduce the bluish cast that can sometimes appear in outdoor photos.