The Lee Filters 4x4 100mm ProGlass IRND 4.5 (15-stop) Filter has been optimized for use with digital sensors and to promote nearly flat attenuation of visible and infrared light, resulting in a perfectly neutral image. When shooting digitally, light at the infrared and ultraviolet ends of the spectrums can be problematic. The ProGlass IRND 4.5 filter has been designed with this in mind, as they absorb more infrared and ultraviolet light than traditional ND filters. The result is a clean, punchier image, with no color cast. Just like the original Lee Filters Super Stopper, it has a 32,000x filter factor that provides a 15-stop exposure reduction. The 4.5 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you can control depth of field and convey movement more easily. This 100 x 100mm ProGlass IRND 4.5 Filter is constructed from scratch-resistant, optical glass for clarity as well as color fidelity and features a built-in gasket. This gasket works with a compatible LEE Filters 100mm System filter holder to help form a seal that is intended to prevent stray light, which could have unwanted effects on exposure, from coming in between the filter and the lens behind it. For efficient use in the field, an exposure guide is included that shows the amount of exposure reduction the 100 x 100mm ProGlass IRND 4.5 Filter provides, corresponding to a range of shutter speed settings from 1/1,000th of a second to 2 seconds before the filter is applied.