Preparing an Image for HDR Toning
The kind of image you feed into HDR Toning affects the results you get. The following tips can help you avoid some of the pitfalls of single-image HDR, and they’re also true if you’re starting from Adobe Photoshop Lightroom 3:
- Start with an image that contains the widest range of tonal detail you can pack into it. Shoot with your digital camera set to capture in raw format, and use the clipping display on the camera LCD to control what highlight and shadow detail makes it into your exposure.
- In Adobe Camera Raw, correct the white balance, then adjust the Exposure and Blacks sliders to drive as much of the usable tonal range as you can inside the highlight and shadow clipping points (see Figure 5). Tones you include will be passed on to HDR Toning, tones clipped out during raw conversion (or not present in a JPEG image) can’t be used or recovered later. (Of course, it’s OK to clip specular highlights.) Don’t bother making the image look perfect in ACR, you’re just bringing along all the important tones for HDR Toning to use later. Leave the image tonally flat; don’t make other tonal adjustments. Also, set ACR Output Options to convert at 16 bits per channel.
- Apply noise reduction. For a raw file, you’ll want to use the astounding noise reduction in Camera Raw 6. While doing this, temporarily increase the Exposure and Fill Light sliders so that you can see the color and luminance noise that exists in the shadows even at ISO 100; that’s the noise you want to minimize so that it’s less visible in the final image. After you’re done adjusting noise reduction values, remember to decrease the Exposure slider value until it isn’t clipping highlight detail, and set Fill Light back to zero.
Figure 5 Highlights (red) and shadows (blue) currently clipping in Adobe Camera Raw as indicated when the clipping display is on (circled), which means I could decrease the Exposure and Blacks sliders a bit
Following these guidelines is critical if your goal is a conventional photographic image. However, if you’re using HDR Toning to make one of those crazy surrealistic images with saturated colors, you can be a lot less picky about the kind of image that you start from; feel free to experiment with any image you want.
Now you can probably see why I set up my image the way I did. Back in Adobe Camera Raw, my number one priority was to make sure there was no clipping of highlights or shadows. That made this image look flat, but I wanted to leave the heavy lifting to HDR Toning. Once the Exposure and Blacks sliders were set, and the White Balance was adjusted, I was ready to send it to Photoshop as a 16-bit image by clicking the Open Image button.
What would have happened if I had used an image where the highlights were clipped? In Figures 6 and 7, you’ll see that I would have lost detail in the sky and in the shadows under the bridge, and the image as a whole is a lot harder to control. It’s pretty ugly.
Figure 6 Intentionally clipping highlights and shadows in this example in Adobe Camera Raw
Figure 7 The best I can do in HDR Toning with the clipped example; details in the sky and deep shadows are gone
Unfortunately, this means that you may get less satisfactory results from fully finished images (such as out-of-camera JPEGs) than from images where you still have access to the complete original tonal range.