Graduated Neutral Density Filter Buyer's Guide
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Landscape photographers, real estate photographers, and architectural photographers all love graduated neutral density (ND) filters for capturing great photographs. Graduated ND filters are best when they are in the form of a filter holder system and square or rectangular filters, which makes sense as we learn how to use graduated ND filters.
Why Graduated ND Filters Are Needed
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Graduated ND filters are used to tame scene dynamic range issues. Well, what is dynamic range and what issues can it cause?
At its simplest, dynamic range refers to the ratio of bright to dark within a scene and how it is recorded on an imaging sensor or film. You can actually measure the dynamic range in a scene by taking readings from the highlights and from the shadows and making note of the difference in stops of exposure.
Our eyes and brain see all of that but we instantly compensate and evaluate without even thinking about it. But, if you go from a bright outdoors quickly into a dark room, you will have a moment of poor vision while your eyes and brain adjust. The image sensor or film can only handle a fraction of the ratio of what our eyes can see.
Graduated ND filters can be positioned so that the densest part of the filter is covering the brightest part of the scene and the clear part over the darkest part, thus lowering the ratio of bright to dark. This gives our imaging device a better chance of recording the scene well enough to be a good photograph.
Types of Graduated ND Filters
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As you could imagine, there are a lot of different situations where graduated ND filters would be useful. Not all scenes will have the same types of dynamic range issues and the areas of light to shadow can also vary quite a bit.
While there may also be some variations within the types, the three types of graduated ND filters are hard-edge ND filter, soft-edge ND filter, and reverse ND filter. Let’s examine these ND grad filters.
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Hard-Edge ND Filters
The simplest form of graduated ND filters are the hard-edge ND filters. These ND grads are dark on one side and clear on the other with a very small transitioning area. The ND or dark part of the ND grad can be 2 stops, 3 stops, or even denser.
The Haida 100 x 150mm Red Diamond Hard-Edge Graduated Neutral Density 0.9 Filter is a 3 stop hard-edge ND filter with a very quick transition area. It can almost be considered a line, the transition is so narrow, but not quite. It fits into the Haida 100 filter holder allowing for precise placement of the transition.
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With a hard-edge ND filter, it is very important to be careful where to place that edge so as not to call attention to the transition itself. Which is why a filter holder system is a preferred method for ND grads since you can slide the filter in and out of the imaging area as well as rotate it around, allowing precise placement.
Hard-edge ND filters are very useful when the transition from light to dark in the scene itself is very defined, such a clearly seen horizon line. Ocean and lake photography or prairie landscapes are examples of a situation for this ND filter.
Soft-Edge ND Filters
Many of the scenes we photograph with high dynamic ranges are not so clearly defined as to where to place the transition area. Architectural studies, cityscapes, real estate photography, and most landscapes or scenic views without a well defined horizon line fall into this category.
As an example of this type of graduated ND filter we have Haida’s 100 x 150mm Red Diamond Soft-Edge Graduated Neutral Density 0.9 Filter is a 3 stop ND grad for their filter holder systems. The Haida Red Diamond ND grads are designed as extremely high optical quality filters with low glare and also very scratch resistant to ensure the best images possible when using them.
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Another situation that makes using soft-edge ND filters a good idea is pretty specific to cityscapes and other architectural scenes. When a tall building or a large wall is silhouetted against a bright sky, a soft-edge ND filter can make it so that we can still get sky detail while properly exposing the structure.
Reverse ND Filters
Reverse ND grad filters are a special design that combines soft-edge ND filters and hard-edge ND filters and has the darkest part of the filter near the center. The clear to dark transition line in the center is hard-edged with the rest of the density fading very softly towards the outer edge.
Haida makes the 100 x 150mm Red Diamond Hard-Edge Reverse-Graduated Neutral Density 0.9 to 0.3 Filter that has a hard-edge center transition to 3 stops that very gradually fades towards the outer edge until the ND is 1 stop.
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What are these types of graduated ND filters used for? Primarily sunsets and sunrises. The reason is because the brightest part of the scene is where the Sun is, with the sky above and the foreground being darker.
Using ND grads like this will let you maintain detail in buildings or vegetation (or rocks) and still get sky detail such as wispy clouds, too. It is a very useful filter for anyone into sunset and sunrise images.
Taming Dynamic Range In One Exposure
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There are some other very good methods and techniques for taming high dynamic ranges in digital photography.
HDR (High Dynamic Range) processing, blending together several images taken at different exposure settings, can result in some outstanding final images, but it requires capturing several exposures and special processing.
Using graduated ND filters will let you accomplish the task of controlling the dynamic range of scenes with single exposures and minimal processing. Make sure to only use very high quality lens filters such as the ND grads from Haida to ensure the best possible images.
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