This K-Series ND65000 Drop-In Neutral Density Filter from H&Y Filters is an ND filter with a 4.8x filter factor that provides a 16-stop exposure reduction. Mounted within an aluminum-alloy filter ring, it is made specifically to fit between a separately available H&Y Filters 100mm K-Series Filter Holder and one of the filter holder’s adapter rings. It darkens the entire image area, allowing you to photograph with a wider aperture or slower shutter speed than normally required. Increasing the lens aperture allows finer control over depth of field and bokeh, making it easier to help isolate the subject of an image. Slowing exposure time helps to convey movement and increase image blur.