Fixing Images with a Digital Graduated NeutrAl Density Filter

© 2002 Lewis Kemper



Mt. Ansel Adams Galvin 2 1/4 view camera mounted on a tripod, Schneider 150mm lens, Fujichrome Velvia, ISO 50, f/32 @ 1/15, slide was scanned on an Imacon Flextight Precision II, image resized to 1,779 x 2,400 pixels, 12.8Mb .tif

© 2002 Lewis Kemper


Most photographers have experienced the challenge of capturing the tonal range found outdoors with a camera when it exceeds the tonal range of the digital image sensor or film. A good example of this problem occurs when shooting a sunset scene with reflections in water, as shown in Figure 23.1. One way of overcoming this too wide tonal range is to use a graduated neutral density filter when shooting the scene. There are various types of graduated neutral density filters, which can be glass, plastic, or gel, and they are available in one, two, three, and more stops. The purpose of these filters is to compress the tonal range or contrast range of a scene into a range that will fit within the limitations of the camera that is being used to take the photo.

Many times though, photos are taken without the benefits of a graduated neutral density filter. In those cases, you may be able to partially rescue the image by using this useful digital graduated neutral density filter technique suggested by Lewis Kemper. Unlike the camera-based filter, this digital technique allows you to more selectively define what gets lightened and darkened, rather than just applying a straight graduated neutral density tone to the photograph.


■ Choose File ^ Open (Ctrl+O) to display the Open dialog box. Double-click the \23 folder to open it and then click the mt-ansel-adams-before.tif file to select it. Click Open to open the file. A quick look at the photograph and you notice that the sky is too bright (it is over-exposed) and the foreground is too dark (under-exposed).


■ As the intent is to use the Multiply blend mode to darken the bright sky and distant mountain range, an adjustment layer is needed. To create one, choose Layer ^ New Adjustment Layer ^ Curves to get the Layer dialog box. Click OK to get the Curves dialog box. Click OK to create the layer as no adjustment to the curve is needed for now. The Layers dialog box now looks like the one shown in Figure 23.3.

When creating the adjustment layer, Levels, Curves, Hue/Saturation, or any other type of adjustment layer can be selected. Creating an adjustment layer allows a blend mode to be set and it automatically creates a mask, which is needed in Step 3.

■ Click in the Blend Mode box in the Layers palette and choose Multiply from the pop-up menu. The entire image looks much darker now as the Multiply blend mode has the same effect as stacking two slides together on a light box — they build up density and the image gets darker.

If the intent were to bring out the details in the darker part of the image, then the Blend Mode should be set to Screen, which has the same effect as increasing the exposure to lighten the image.



Since 1980, Lewis Kemper has been working as a freelance photographer. Since he received a BA in Fine Art Photography from George Washington University, Lewis has not only created a phenomenal portfolio of photographs, but he is also a prolific writer who has written several books, published many magazine articles, and is currently a contributing editor to Outdoor Photographer and PC Photo magazines. His photographs have been shown or collected nationally in galleries and museums,


■ To create the effects of a graduated neutral density filter, click the Gradient tool (G) in the Tools palette. To select a gradient, click in the Gradient Picker in the Options bar to get the Gradient palette shown in Figure 23.4. If the palette does not look like the one shown in Figure 23.4, click the menu button in the Gradient palette and select Reset Gradients; click OK when asked Replace current gradients with the default gradients?

Click the Black, White gradient, which is the third gradient from the left on the top row.

■ To lighten the bottom part of the image, press Shift and click in the image about half way up the image and drag the cursor all the way to the top of the image. Pressing Shift makes the gradient run perfectly straight up the image. The image looks much better now as the gradient acts as a mask to the second layer — the blacker the mask, the more the second layer is hidden and the lighter the image is. Conversely, the lighter the mask is, the more the second layer is allowed to darken the image.


Now here is the advantage of this technique over using a graduated neutral density filter when shooting. After the initial gradient has been drawn in

Step 3, you can now retouch the image by using the Brush tool set to a low Opacity of around 10% and painting the mask to lighten the trees and make the transition look more realistic. Using a real filter in the field would make the treetops darker than the bottoms, so this method is a definite advantage over the conventional method. After some painting on the mask, your image should look similar to the one shown in Figure 23.2.

This outlines the steps you can take to improve this image. You can now continue working on it as you would any other image and adjust it further as you like.

As an alternative to shooting a single photo and making the best of it by using this useful technique, you should also consider taking two different exposures of a scene; one exposed for the highlights, and one exposed for the shadows — then use Technique 28.


such as The Cornell Museum, The Frederick S.Wight Gallery, The Baltimore Museum of Art, The Princeton Gallery of Fine Art, The Popular Photography Gallery, The Ansel Adams Gallery, Photographer's Gallery, and The Yosemite Valley Visitor Center. Lewis teaches Photoshop classes for Palm

Beach Photographic Centre, Santa Fe Workshops, and Hoot Hollow Institute. He also runs a custom print service using his digital skills to create fine art prints for photographers. To learn more about Lewis' work and the services he offers, visit his Web page at www.

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