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Basic Photoshop

Create a Split ND Effect with a Layer Mask

This Article Features Photo Zoom

This image is exposed for the dark foreground.

The graduated split neutral density filter has been a must-have filter for nature photographers for years. The filter basically has a dark gray top half and a clear bottom half, with a gradual transition from gray to clear, and comes in a variety of strengths and gradations. Placed in front your camera’s lens it allows you to capture detail in the bright highlights in the top half of a scene (usually the sky) and still capture detail in your shadow areas. With the advent of digital photography, photographers are able to simulate this effect using a variety of techniques, from HDR processing to the shadow/highlight adjustment in Photoshop to liberal use of the recovery and fill light sliders in Adobe Camera Raw.

For me, the easiest and most natural looking way to digitally simulate the use of a split ND filter is to take two photos of the same scene, one exposed for the highlights and one exposed for the shadows, and then combine the images in Photoshop. This is one of the first Photoshop techniques I used on a regular basis when I made the transition to digital imaging, and I find it is still a quick and useful technique. This procedure uses a layer mask, which I’ll explain in some detail, but if you’re not familiar with layer masks, you might want to read my previous post “Basic Photoshop – Layer Masks” (Outdoorphotographer.com)

This exposure is exposed to capture detail in the sky.

Step one is to remember to take two or more photos when you are out shooting. Use a tripod, so your images will align perfectly and take one exposure that captures all the highlight details and one exposure that captures all your shadow details. These can be 2, 3, or sometimes 4 stops apart. For the highlight shot, check your histogram and confirm you are not clipping any highlights. For the shadow shot, make sure you are not clipping any blacks. Here are two shots from a scene in western Connecticut I shot a few weeks ago: (Above: image 1, Left: image 2)

To get started, open both images in Photoshop, then copy the bright image onto the dark image. The best way to do this is to use the move tool (top tool on the tool bar). Click on the bright image, hold down the shift key (this will align the images) and drag the bright image on top of the dark image. You can now close the bright image because we’ll be working with just the dark image which now has two layers, one bright, one dark.

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