Understanding HDR Toning in Adobe Photoshop CS5
True high dynamic range (HDR) software, such as Merge to HDR Pro in Photoshop CS5, offers several techniques for compressing the extended tonal range of bracketed multiple exposures into the limited dynamic range of a monitor or printer. Unprocessed HDR images tend to look flat and dull because so many tones are packed into a relatively narrow range. A primary job of true HDR tools is to bring out the contrast that creates the snappiness and punch you see in one-shot photographs, while preserving the extended shadow and highlight details that were captured with bracketed exposures.
Many people like to use true HDR tools to push a image beyond a conventional photographic appearance and create the more extreme look of heightened colors and local contrast that is now often associated with HDR. Before Photoshop CS5, the tools to achieve popular HDR effects were available only by merging bracketed exposures. Adobe added HDR Toning to Photoshop CS5 in part so that you can create HDR-style effects using similar tools and just one photo. While HDR Toning is not true HDR, its tools are useful when you don’t need extended dynamic range but you do want that look.
Using HDR Toning
Because you don’t need multiple images for HDR Toning, getting started is as easy as applying an effect. Start by opening a flattened, non-raw, RGB- or grayscale-mode image, then choose Image > Adjustments > HDR Toning.
In my example, I start with a landscape photo that appears to be dark with muted colors and low contrast (see Figure 1). Later in this article, I’ll talk about why I chose to start from an image that looks this flat.
Figure 1 My original image
The options in the HDR Toning dialog box are almost identical to those in the Merge to HDR Pro dialog box, so if you’ve already used Merge to HDR Pro, you already know what to do. If you haven’t used Merge to HDR Pro, let’s quickly take a look at the HDR Toning controls.
The fastest way to start is to choose a preset from the Presets pop-up menu at the top of the HDR Toning dialog box. Pick one with a name that resembles how you want the image to look, such as Photorealistic or Surrealistic. Don’t expect the image to look amazing at this point because each image’s tonal qualities affect the results. Instead, expect the presets to be starting points, and then start playing with the options.
There’s a Method pop-up menu with four choices, but most of the time you’ll find Local Adaptation most useful; all the presets are based on it. Local Adaptation options fall into four groups: Edge Glow, Tone and Detail, Color, and Toning Curve and Histogram. Generally, it’s best to start in the Tone and Detail group to set the overall look of the image. Set Exposure first because it controls overall brightness; then adjust Shadows and Highlights to set the brightness of the dark and light regions of the image, respectively. Gamma controls overall contrast, while Detail enhances sharpness through microcontrast (very local contrast). For my image, the Default preset already improves the image (see Figure 2).
Figure 2 The image with default HDR Toning settings
Because the image starts out a bit dark, I increase the Exposure value. This reveals the challenge here: preserving detail in the landscape areas without blowing out the sky. I increase the Shadow value to lighten the dark landscape, and significantly decrease the Highlight value to move the sky tones closer to the landscape tones. I gradually drop the Gamma value to boost contrast to the level I think is about right for a believable image (see Figure 3).
The Edge Glow options control the size of the local adaptation zone; they answer the question “How local do you mean?” Radius controls the local adaptation area in pixels. Strength defines what local means for tones; as long as two pixels’ values are within the range set by Strength, they’re considered part of the same brightness region. In my example, I keep my Edge Glow settings low because I’m going for a natural photographic look; using high values is one way to get that wild HDR look.
The final image looks much more colorful than the original. While part of this is because increasing tonal contrast also increases color contrast, I also raised the Vibrance and Saturation values in the Color options group. If raising Saturation makes colors too garish, try raising Vibrance instead, because Vibrance intelligently avoids boosting colors that are approaching oversaturation.
Once I’ve got the overall image down, I fine-tune overall contrast using the Toning Curve and Histogram. I won’t go into detail about this because it works very similarly to the Curves panel in Photoshop. Because the curve represents such a long tonal scale, I find that I have more detailed control over contrast if I work with straight segments by selecting the Corner check box when a point is selected.
Figure 3 The final image and its HDR Toning settings
When I’m done, before I click OK, I like to click the settings icon to the right of the Preset pop-up menu and choose Save Preset. I then name and save a preset, so that I can quickly return to these exact settings later if I want to start over later. Finally, I click the OK button. I can then work with the image further in Photoshop.
In my final image, my use of HDR Toning brings out tonal details in both a relatively dark landscape and a very bright sky without having to resort to gradient masks or manual dodging and burning. This is made possible largely through the Toning and Detail options and the Edge Glow options.
I could push the HDR Toning options a bit further and come up with a more expressive, fantasy-style HDR image (see Figure 4). While it’s not my thing, the capability’s there for everybody who wants it, and apparently a lot of people do.
Figure 4 A version that uses more expressive HDR Toning settings