Basics of Exposing with a Grad ND Filter

In simple terms, a neutral density (ND) filter cuts down on the light hitting your sensor. A full ND reduces exposure over the entire frame while a graduated (grad) ND reduces exposure over some of the scene. This post will go over how to set your exposure when using a grad ND filter.

If you haven’t already, check out the first post on Using Graduated ND Filters.

Exposure reduction of graduated ND4 square filter

In this soft-step grad ND, the transition between light and dark is spread out over a large area. There are also hard stop filters that have a quick transition from dark to light. Soft steps work well when there are things covering the horizon such as trees or mountains. A hard stop filter works when there is a clear horizon, like over the open ocean.

Choosing between an ND2, ND4, and ND8 filter depends on the dynamic range of the scene. In a cloudy scene where the sky isn’t much brighter than the foreground, you may only need a 1 stop reduction from an ND2 filter. On a bright, sunny day where the sky is much brighter than the foreground, you will need an ND8 to bring out details in the foreground shadows.

Of course this is just a quick, casual way of picking the right filter strength. If you’re more technical, you can meter in both the sky and the foreground and determine the number of stops between the two. Using center-weighted average metering mode works better than evaluative mode to accomplish this.

ND Filters

One of the newest additions to my ever-growing bag of gear is a set of Neutral Density (ND) filters. The graduated (grad) ND filters are used to darken bright areas of the scene, evening out the exposure. Full ND filters allow you to darken the entire frame to get a longer exposure when there is bright light.

Goja complete neutral density ND filter set with with ND2, ND4, ND8 grad and full square filters

The sensors in today’s digital cameras (and film as well) have a dynamic range that is nowhere near what we see with the human eye. This image shows the difference between a scene with and without the grad ND. The filter used is an ND8, or three stops of exposure reduction. The ND4 and ND2 can reduce the exposure by 2 and 1 stop, respectively.

Landscape scene with and without a graduated neutral density filter.

Notice how the lower parts of the image has a similar exposure, while the scene gradually darkens towards the top where it’s covered by the ND filter. This scene doesn’t show the true power of the filter because it was already evenly lit. The best use is when the sky is bright, but you still want detail in a dark foreground.

This image darkens the background and allows for a bright, flowery foreground. Without the filter to darken the sky, there would be almost no detail in the clouds and even the mountains would be much brighter. The placement of the filter here actually lowered the exposure slightly all the way down the to near the flowers.

Landscape photograph using graduated ND filter

The full ND can be used under bright light when you want a multi-second exposure, but can’t stop down the aperture or lower the ISO. The ND2, ND4, and ND8 darken the entire exposure by 1,2, and 3 stops, respectively. Below is an example of using the filter during bright, sunny conditions.

photograph of blurred water using full ND square filter

Here is an affiliate link to the filters I purchased. Goja Complete ND Filter Set on Amazon.

While they aren’t of the highest quality, they are still good for learning. In the future I plan to purchase a set of Singh-Ray filters.

Check out how to expose using your grad ND filter.