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Monday, March 1, 2004

Tame Lighting Extremes


Nature often serves us splendid scenes, but with light that won‚’t cooperate with our camera‚’s and film‚’s abilities. Here‚’s how to bring those conditions under control.



Filters Still Work In A Digital Age

A technique that has become popular for getting the right exposure in the sky and foreground of an image involves using the computer. By having your camera on a tripod and making two exposures at the scene (one for the bright sky and one for the dark foreground), you can meld aspects of each exposure together to make a perfect finished image.

Filters Still Work In A Digital Age
Some scenes, like sunsets with land or scenics with deep canyons, have a much wider contrast range than film or digital media can record. If we shoot for the highlights, we lose the shadows. If we shoot for the shadows, the highlights are gone. To get around this, use imaging software to combine two frames of the same subject, one exposed for the highlights and a second one exposed for the shadows. If the camera and subject remain perfectly still between exposures, the two images can be merged in a computer later. Either a film or digital camera will work. Here's how to do it.

When shooting the pictures:
1 Use a solid tripod so the camera doesn't move. You want the two images to line up precisely in the final photo, and if you think you might have bumped the tripod between frames, start over. It's easier to begin again than it is to realign the two images in the computer.

2
Take the first shot with an exposure that favors the highlights to lay the groundwork for the image. If a critical area of your subject is white, as with a waterfall, clouds or snow, expose to avoid blowing out your highlights. The beauty of the two-shot system is that we can underexpose this shot to maintain our highlights without having to worry about the loss of shadow detail!

3 The second shot is just for the shadows. Our aim here is to provide enough extra exposure to improve shadow detail. The "right" amount of extra exposure is an aesthetic decision as much as a technical one. While one stop often works, two or more stops also can be appropriate, depending on the scene. Bracket your exposures. That way, you'll have a range of shadow exposures from which to choose. If you're shooting digital, take advantage of your camera's LCD to check your results.

When assembling the pictures:
To create your final, long tonal-range image, use a program that supports layers, like Adobe Photoshop and Photoshop Elements, Jasc Paint Shop Pro, Deneba Canvas and others.

4
Choose the best of your highlight exposure brackets, and the image that provides the amount of detail you want in the shadow areas (look at both tonal and color information). For the latter, ignore the highlight parts of the image when making your choice. If you shot film, make a scan of both images.

5 Open your shadow image, and use the Save As command to make it the basis of a new file. Use a new name that helps you remember the image, such as "Bridalveil Falls Combined."

6 Open the highlight file. With Adobe products, click inside the image with the Move tool; drag and drop it onto the shadow file while holding down the Shift key. A copy of the highlight image forms a new layer within the shadow file, and the Shift key makes the new layer automatically line up with the original layer beneath it. With other software, you may need to copy and paste using the menus.

7 Now comes the fun part. We're going to paint in the extra shadow detail only where we want it in the highlight image. Go to the Layer menu and find the command Add Layer Mask (the exact names vary by program, but they're all similar). You'll see a second set of choices—Hide All and Reveal All. Choose Reveal All.

Use a soft-edged brush with black paint to go over the image's shadow areas (you must be in the layer mask in the Layer palette; if black or a color appears on the photo, you're not in the layer mask). As you paint, you'll see the lighter shadows from the lower image appear as the black paint hides or masks those areas of your highlight image layer. The highlight image isn't erased; the layer mask can be adjusted by painting white to bring back the layer, black to hide it again. (If the two layers don't line up as well as you'd like, see #8.)

Your photo is now at your command. You can paint in as much or as little as you like. If your software doesn't support masks, use the Eraser tool to remove parts of the highlight layer so the lightened shadow layer can show through.

The key to the technique is hiding your tracks, especially at the edges between highlight and shadow areas. Go over these edges, going back and forth with white and black paint while using a soft brush until they look right to you.

8 One last note: In spite of our best efforts, the highlight and shadow images may be slightly misaligned. This is especially true with film, as neither mounts nor scanners have precise alignment. If that happens, use the Move tool to move the top layer until it lines up with the bottom layer. Temporarily reducing the layer's opacity and zooming in will help, as will practice.

Sometimes, the two images still won't match. In that case, line them up the best you can, and make judicious use of the Cloning tool to fix bad gaps.
—Zachary Singer



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