1、Variable ND Filter: The adjustable neutral density filter features a combination frame that allows frame to rotate, causing the lens to rotate in relation, achieving a variable ND value effect. By turning frame, we can observe the lens transition from light to dark. 2、Wide Compatibility: The adjustable ND filter utilizes the principle of stacking 2 CPL filters to achieve its adjustable capability. The recommended usage range is ND2-ND400, higher density ranges such as ND1000 and ND2000 are not achievable. 3、ND2-ND400 Filter: Attach it to the lens and point it at the sky or a bright area. Rotate from the minimum to maximum setting while watching color changes in the viewfinder. When you notice uneven light reduction, note the corresponding scale position, as it indicates where to switch for long exposure. Subsequent ranges should be set for longer exposures to eliminate X shadows, typically requiring over 4 seconds for high density ranges to reduce noticeable unevenness. 4、Usage Instructions: Uneven light reduction is not a quality issue but a result of Moore fringe. Sufficient long exposure time can eliminate the X shadow. The maximum position is the limit, as you approach ND1000, it becomes significantly unusable. The recommended effective range for the adjustable ND filter is ND2-400. 5、Long Lasting: Variable ND lens filter ND2-ND400 is made of shock resistant tempered optical glass with an aluminum alloy frame, it is lightweight, long lasting and almost unbreakable. Item Type: Variable ND Lens Filter ND2-ND400 Material: Optical Glass, Aluminum Alloy 1 x Variable ND Lens Filter ND2-ND400 1 x Storage Case