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Here’s a poor-man’s version of CS2’s “Shadows & Highlights” feature for older versions of Photoshop. If your camera tends to expose for highlights (and therefore underexpose subject matter), or if your images have too much contrast, use this to selectively adjust the exposure of the image’s underexposed (or overexposed) areas.

Even if you haven’t blown your two CS2 licenses on desktop machines, leaving you on the road with a laptop and a leftover (but still legal) copy of PS7, this approach actually provides more control than Shadows & Highlights.

Macintosh key commands are indicated; Windows users should by now be adept at translating. Menu items are from PS7.

1. While holding the Option key, select Image->Duplicate…
2. In the duplicate image, apply a mild Gaussian Blur, e.g. 2-4 pixels depending on resolution.
3. Press Cmd-M (or Image->Adjustments->Curves…) to access the Curves dialog; drag both control points horizontally toward the middle of the line, until the image’s dark and light areas are well defined. Specifically, be sure the areas you want lightened are very dark, and the areas you want to stay the same (or darken) are very light. The image can and should be heavily posterized, with blown-out highlights and black shadows — you’re just making a selection mask here, not adjusting the final image. Click the OK button to apply the curve correction.
4. Press Cmd-Shift-U (or Image->Adjustments->Desaturate) to convert the image to grayscale.
5. Cmd-A, Cmd-C (or Select->All, Edit->Copy) to select the canvas.
6. Click in the original image to bring it to the front.
7. Select Window->Channels to display the Channels palette.
8. At the bottom of the Channels palette, click the “new channel” icon.
9. Cmd-V (or Edit->Paste) to paste the greyscale image into the new channel.
10. Now drag the new channel to the dotted-circle icon at the bottom of the Channels palette. (Or, Select->Load Selection… and then pick the new channel from the Channel pulldown.) Important: The image’s highlights are currently selected. Assuming you want to operate on the shadows, press Cmd-Shift-I (or Select->Inverse) to invert your selection.
11. Select the RGB channels with Cmd-~ (or click the RGB channel in the Channels palette).
12. Press Cmd-H to hide the marching ants.
13. Bring up the Curves palette (Cmd-M) and adjust to suit. For example, click to add a control point in the middle of the line and drag either up/left or down/right (depending on whether your palette is configured with dark at the 0,0 or 255,255 corner, respectively).

You can of course jump into Quick Mask mode prior to the final Curves correction to hand-edit the selection, but in most cases this shouldn’t be necessary. Note too you can re-load the selection from the Alpha channel to operate individually on the shadows or highlights.

This technique actually gives you more control than CS2’s Shadows & Highlights command, because you have direct access to the selection, and to Photoshop’s entire complement of editing tools, rather than simply an exposure control.

Screenshots are left as an exercise for the reader. (Hey, I’m on vacation.)