Of all the colour conversion filters the Series 81 filters are the best for everyday use. Available in 5 intensities, they warm up light gradually, thus responding well to lighting conditions which photographers confront most often. This filter reinforces warm lights, such as dawn or dusk, especially if the subject is well-suited for it; like an autumn forest or wheat fields. Please note: A Cokin adaptor ring (sold seperately) & Cokin Z Pro Filter Holder (sold seperately) are required to use this filter