Many sports, nature and astro-photographers use 35mm cameras because the wide selection of telephoto lenses make it easy to get close to the subject. However, longer telephoto lenses, particularly zoom lenses, often have a smaller maximum aperture making them slow and difficult to focus in low light. A Beattie Intenscreen™ bright focusing screen will increase image brightness by 1 - 1½ stops making it easier to focus on distant subjects, even when using a telephoto lens.