Saturday, September 24, 2011

Graduated Neutral Density Filters

Graduated neutral density filters, sometimes called split neutral density filters or grad nd’s, come in a variety of shapes, sizes and densities and are used mostly by landscape photographers to control the exposure range of an image. One half of the filter is of a neutral density which reduces the exposure of bright areas to reduce or eliminate clipping. Some would say it extends the dynamic range of your camera and I wouldn’t necessarily disagree with that but it might be more correct to say they reign in the exposure latitude by creating a manageable balance between the highlights and shadows.

The filters typically come in 4 stop (1.2), 3 stop (0.9), 2 stop (0.6) and 1 stop (0.3) densities and are hard-split or soft-split. Hard split have a more defined abrupt transition from nd to clear whereas soft split have a more gradual transition. These filters come in square, rectangular and screw-on. The rectangular filters are most popular as they allow you the freedom to move the transition in the frame whereas the transition on screw-on filters is fixed, it will remain in the middle of the frame.

There are considerable resources already on the web about these filters so rather than repeat all that I thought I’d continue on with some advanced techniques you can use when using these filters.


Techniques – Aperture

The use of aperture is more distinct when shooting with hard-split rather than soft-split filters. Simply put by opening wide you can soften the transition and closing down will show the transition to be more defined. This is an image I shot with a 1.2 hard split nd grad……

“A New Day Begins……”



Techniques - Stacking Filters

You can create a variety of combinations of grads by stacking filters. Stacking filters means sandwiching two or more filters together, using their combined densities to achieve the exposure control you desire. For example by stacking a 0.9 and a 0.6 here I came up with a 5 stop nd grad……

“Morning Has Broken”




Many variations of stacking can be accomplished for example if the filters are large enough you can stagger their transitions.

Techniques - Feathering

Other techniques would include “feathering” where by you move the filter as the image is exposed. This would be effective when a slower shutter speed is used and can be used to soften or create a larger edge.

This is an image I shot to show the comparison between single filters and stacked filters using a 0.9 and 0.6 soft split filters.

filters

There are also other types of nd grads as variable, Center-spot and reverse nd grads but these are less common and perhaps a topic for another day.

If you have any questions, would like to provide some input or wish to discuss this further please leave a comment I will get back to you. Thank You for stopping by!