Graduated Neutral Density Filters (ND-Grads)
For a very long time, graduated neutral density filters (ND-grads) were an essential part of every landscape photographer’s kit. These rectangular filters are dark on one end and then gradually fade to clear. The primary use of ND-grads is to compress extreme tone range in landscape images, which can easily occur during sunrises and sunsets. By placing the dark part of the filter over the brightest part of your scene, you could “hold back” a bright sky while still getting a decent exposure of the darker foreground.
The challenge with using ND-grads has always been getting proper placement, and knowing how strong of a filter to use. Moreover, because these filters have a defined horizontal boundary, they can be really tricky to use in scenes with dominant foreground objects that protrude into the sky, such as trees. Another drawback of ND-grads is that they can cause artifacts from reflections or poor-quality construction.
Many modern digital cameras now boast dynamic ranges of up to 14EV (compared to slide film which may have had 6-8 EV), meaning that you’re able to capture more tones in-camera without clipping them. The use of HDR techniques also reduces the need for ND-grad filters. If you’re in a scenario where you have to get the exposure perfect in the as-shot image (such as JPEG or video), then ND-grads are still useful. However, I find that I no longer use mine, as it’s easier to adjust exposure on a RAW image than properly position a grad filter in the field.
Verdict: Between the great dynamic range of modern cameras and the advent of HDR photography, most photographers don’t need to use ND-grads anymore. They are still useful for JPEG/video shooting or extreme conditions.