This filter has the same percentage light transmittance as the Tiffen 0.6 (optical density) neutral density filter. A ND4 filter cuts all light by 75%.  This forces the Hero3 to slow its shutter speed.  An ND filter is often used to reduce or eliminate prop blur for general aviation videography and minimize the "jello effect" experienced in some radio controlled applications.  

Consider using this filter if you are filming the following sports:

• High vibration motorsports
• Multi-rotor RC 
• General aviation

The Marumi ND4 Filter reduces the light volume without altering whole colour tones, allowing you to delay your aperture by two stops. The filter allows you to lengthen your shutter speed without adjusting your aperture to create a fluidity effect. The ND4 grey filter is suitable for use outdoors, along the seaside or in the mountains covered in snow. Due to its thin design, the Marumi grey filter can be used in conjunction with wide-angle lenses without causing vignetting to the image.