Exposure for Landscape Photographs
How to Use Graduated Neutral Density Filters
Knowing how to use a graduated neutral density filter is a key skill for either traditional or digital landscape photography.
One of the trickiest aspects of landscape photography is to capture the wide range of brightness values that are typical of the most interesting and attractive scenes. How can we expose correctly for both the foreground and sky at the same time?
The graduated neutral density filter
The graduated neutral density filter, often known as the ND Grad, is the key to solving this conundrum. In practice the ND Grad’s main value is that it helps preserve detail in the sky as well as in the foreground. Instead of appearing as amorphous white streaks or grey blobs, clouds retain their intricate shades and natural patterns, the kind of difference that distinguishes good, satisfying shots from disappointments.
The ND Grad usually takes the form of a rectangular transparent sheet, dark at one end and clear at the other, which slips into a frame attached to the front of the lens. The filter can move up and down within the frame, and the frame can rotate so that the dark end of the filter can be lined up with the brightest area of the composition, usually the sky at the top of the shot.
Types of ND Grad filters
ND grad filters vary by the amount of difference between the dark and clear ends. Manufacturers use different terminology, but typically offer filters that compensate for one, two or three stops of difference in brightness. An in-camera or separate light meter will show you how much the correct exposure varies for the brightest and darkest parts of the scene, and therefore which filter to use.
ND Grad filters also vary by the nature of the transition from dark to light, which may be “soft” or “hard”. A hard transition filter is best where there is a clear, straight horizon between the dark and light parts of the composition.
A variation suitable for rather specialised and precise compositions is the reverse ND Grad, which has its darkest band in the middle and fades towards each end. This filter can work well for sunrise and sunset shots where for a few minutes the brightest part of the sky is exactly on the horizon.
Leaving the reverse ND Grad aside, a complete set of ND Grads to cover all eventualities would include a soft and hard transition filter at each of one, two and three stops, a total of six filters. Of these, the two-stop soft version is probably the most widely used and would be a good starting point for someone new to this approach.
Camera filter manufacturers
Lee filters have a good reputation and are probably the most commonly credited by professional landscape photographers in books and magazines. Other manufacturers such as Cokin offer significantly cheaper alternatives.
The less expensive filters may introduce a slight colour bias, though it is usually almost imperceptible; they may be physically smaller than Lee filters which can result in some vignetting (dark corners) when used in wide angle shots with large diameter lenses, 77 mm or larger; and they may be more prone to scratching. But any ND Grad filter is a valuable addition to the landscape photographer’s camera bag and the cheaper ones are well worth considering as an alternative to Lee filters for the budget conscious.
Digital filter effects
One of the advantages of digital photography is that the effects of many traditional filters can be replicated on the computer, long after the shoot is finished. Photoshop and Lightroom make adjustments like warming up or cooling down almost trivially easy.
To a certain extent it is possible to mimic the effects of the ND Grad, particularly if you work from RAW images rather than jpegs. But that's another story, and doing so is difficult to pull off convincingly. As always, shooting landscapes with a view to rescuing poor or mediocre shots afterwards at home is unwise and rarely successful.
Knowing how to use a graduated neutral density filter was, is and probably always will be a key skill for landscape photography.
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