Cokin Filter Z-Series 100mm Full ND4 Z153
How to use a Gradual Neutral Grey filter ?
• To decide which filter density to use, you just need to measure – spot measuring with your camera or with a separate spot-meter – the clear zone where you wish to keep the detail and the zone that will be used for the final exposure. Then count the number of stops difference – at constant speed. For a 2 stops difference you will need a density of 0.6.
• Take care to modulate your effect depending on the subject; for example, a reflection must be less bright than its source. Finally, depending on the way that the zone separating light and shadow presents itself, you will choose either a short or long transition zone filter.
• You must then adjust the filter – close the diaphragm as much as possible by pressing the depth of field preview button to better see the transition zone in the viewfinder while adjusting the filter vertically until its transition zone corresponds perfectly with the light intensity line of your framing. The effect of the filter depends both on the lens and on the diaphragm setting. The more the aperture is reduced, the more the effect of the graduated shading will be noticeable. Note that the capture settings has an impact on what the filter can do.
• Expose for the foreground. With experience, you will determine at a glance the filter you need to use and it will only take you a few seconds to adjust it efficiently with precision. The best practice would be to always carry the three densities to fit almost any lighting condition.