For landscape photography, it’s hard to beat the usefulness of graduated neutral density filters, also called graduated ND filters or GND. There are several types of ND filters, though, soft and hard edge being the two most common. When and how should you use soft vs hard graduated ND filters?
What’s the Difference?
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Neutral density filters (ND filters) add density to the light path of an exposure. Density means it attenuates light, neutral means it has no color cast. A typical example of ND filters could be either screw in or part of a filter holder system and will be a solid amount of density all the way through.
Graduated ND filters are dense on one side of the filter and clear on the other side and a gradual transition from light to dark. The difference between soft vs hard graduated ND is how quickly the transition is made. If the transition uses a lot of the center of the ND filters, they are soft edge, if the transition is pretty quick, not taking up much room, they are hard edge ND filters.
Most of the graduated ND filters will be in a filter holder system, the filters are square or rectangular and they fit into a holder that allows you to rotate and slide the ND filters into the exact position you need them.
Here is an example of a filter holder system:
In addition to the soft vs hard graduated ND filters, there are also reverse GND with one side having the ND part lighter towards the outer edge in a very soft transition and a very hard edge in the center. Another type is the horizon line ND filter with a dark strip of harde edge right across the center and clear on the outer to sides. One last type are medium edge ND filters.
When to Use a Soft Graduated ND
The Haida Red-Diamond 100x150mm soft edge GND filter for their M10 filter holder system is an example of a high quality GND filter.
What situations do soft graduated ND filters work best? Any scene with one part of the image, either vertically divided or horizontally, that is substantially brighter than the other. This causes exposure balance or dynamic range concerns.
In order to see good detail in the highlights, the shadows, and everything in between, we either need to use the bracket and merge HDR method or we pull down the highlights into a range where we can easily balance them with the shadows with ND filters.
The soft edge comes into play as we examine our scene to see where to place the transition from clear to density of the filter within the scene. If there is not a straight line that differentiates the brighter side from the darker, we use soft edge ND filters.
Examples of a scene that would need soft vs hard graduated ND filters are landscapes with a bright sky but no clear horizon, such as a mountain range or forest. A cityscape would also qualify since these can often resemble a mountain range.
Upside down, a case could be made for using one indoors such as in a cathedral where we want to have good detail on the floor as well as in the vaulted or domed ceiling.
When to Use a Hard Graduated ND
The Haida Red-Diamond 100x150mm hard edge GND filter is what a hard GND looks like. If we would use soft graduated ND filters with scenes that have no clear horizon or dividing line, then when to use a hard graduated ND filter is when the scene DOES have a clear dividing line.
An example that comes to mind is twilight or Blue Hour photography. The sky will be brighter than the ground, so attenuating the sky in order not to lose ground level detail is in order. Sunrise or sunset scenes that have the Sun pretty far from the horizon also work.
So would architectural images, perhaps even used vertically to balance a building in shadow against a sky or other brightly lit buildings. Regardless of the actual scene, the hard edge transition line is placed on the scene dividing line, whether that’s the horizon or some other edge.
When to Use Other Types of ND Filters
For a transition in between soft vs hard graduated ND filters, there are medium edge ND filters, such as the Haida 100x150mm medium edge GND filters that can be used in many other photographic conditions.
For that special situation listed earlier with the Sun right on the horizon during the climax of Sunrise or Sunset, it’s hard to beat the Haida Red-Diamond horizon graduated ND filters, pictured above.
Open Up Your Creativity
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You already know why graduated and solid ND filters themselves are so useful for landscape photography, using them in a filter holder system opens up all sorts of creative opportunities.
Only polarizer filters might be more valuable in your landscape photography camera bag. As a helpful note, many of the filter hldrs also fit circular polarizers, even allowing you to combine filters together for yet more creative control.