Adobe Photoshop CS5 for Photographers - Martin Evening [182]
Figure 7.6 On this page you can see a comparison between a single edited image, using an optimum exposed photograph (top), processed via Camera Raw and output as a 16-bit file. Below you can see the HDR edited version that was converted to make a 16-bit low dynamic range image. At first glance the difference is quite subtle. I did after all try to get the two images to match as closely as possible, but you should notice better tone and detail contrast in the rocks in the HDR converted version. The difference was more noticeable though when I examined the shadow areas. In the enlarged close-up views you can see there is much more image detail and virtually no shadow noise in the bottom image.
Exposure slider
It is impossible to represent an HDR image on a standard computer display, which is why the Exposure slider is available as a slider at the bottom of the document window. It allows you to inspect an HDR image at different brightness levels. Since the display you are using is most likely limited to a bit depth of 8-bits, this is the only way one can actually ‘see’ what is contained in a high dynamic range 32-bit image.
1.
I began here with an HDR image that was produced by merging together a bracketed sequence of three photographs, shot at 2 EVs apart. To reduce any movement in the individual exposures, the camera was mounted on a tripod and the pictures were taken using a cable release. This first screen shot shows the merged HDR file as it appeared in Photoshop in 32-bit per channel mode with the Exposure slider adjusted so that I got to see a reasonably good view of the HDR image. In 32-bit per channel mode one can use the Exposure slider to preview the HDR image at different levels of brightness. Here, the Exposure slider allowed me to adjust the preview as I focused on retouching different parts of the picture using the clone stamp tool prior to making the HDR tone conversion.
2.
To convert this high dynamic range image into a low dynamic range version I had two options. I could go to the Image Mode submenu and chose 16-bits / Channel, or choose Image HDR Toning… Either of these methods would open the HDR Toning dialog shown here. Of the four tone mapping options that are available in this dialog, I find that the Local Adaptation method usually works the best and in this screen shot I left all the sliders at their default positions. Although the image doesn't look all that great just yet, this is certainly quite an improvement upon how the default HDR converted image preview looked in previous versions of Photoshop.
3.
Here I adjusted the HDR Toning sliders to produce what might be called the ‘illustration look’ that is favored by many HDR photography enthusiasts. If this is the type of effect you are after, I don't think the Photoshop HDR Toning adjustment is really as capable as, say, Photomatix Pro, nor is it as simple to configure, but Photoshop CS5 can now be made to produce the rather obvious ‘HDR toned effect’. Looking at the settings shown here, I set the Radius slider to 100 pixels and raised the Strength to 0.80. I took the Gamma slider to 0.7, set the Exposure slider to +1.35 and the Detail slider to 150%. I then reduced the Highlight slider to -100% and increased the Saturation slightly, setting it to 25%.
4.
In this last step the aim was to produce a more natural-looking result. To start with I set the Radius slider to 300%. This was done to create much wider halo edges. I also took the Strength slider back to it's previous default setting of 0.52 and the Gamma slider back to the default 1.00 setting. I reduced the Detail slider to 120% and the other settings, including the Exposure, Highlight and Saturation sliders were left at the same positions as in Step 3. I then adjusted the Toning curve to fine-tune the final tone mapping and was able to refer to the Histogram panel in Photoshop as I did this. Lastly,