How to Create High Dynamic Range Images

Continued...

How to Create High Dyn...

Our step-by-step guide teaches you how to navigate the most popular HDR programs, including one you may already have at your fingertips.

By Jack Howard Posted September 19, 2006

CREATING AN HDR NEGATIVE

Now for a confusing bit of information: your monitor cannot properly display HDR images, and your printer cannot properly print them out. You've got to Tone map the HDR image, and crunch it back down into a Low Dynamic Range format that your computer and printer can handle for final output. This particular LDR image will maintain the expanded tonality and detail of an HDR image. Let's call this HDR file, with its massive 32-bit depth, the HDR "negative." In order to view it, it must be "developed" in the tonemapping tool. The computer cannot display the true HDR image correctly, because a massive number of potential color values for every pixel is assigned to each pixel, but each pixel's final value is dependent upon the values of its local pixel neighborhood, each of which also has an enormous amount of potential color values dependent upon the pixel values of the first pixel we mention. Got it? So, until the HDR is "developed" in the tone mapper, none of the pixel values are locked in, and thus, it is not able to be displayed properly.

So, now we've got this HDR "negative" image that our screen cannot display properly; but notice that little navigator window that opened when your HDR image was generated? This window will give a preview of how the Tone mapping tool can develop your HDR "negative." (See above)

Now for the fun part. Under the HDRI dropdown menu, select "Tone mapping." (See above) A preview window opens, showing you what your HDR will look like once it is Tone mapped and crunched back down into Low Dynamic Range space for printing and display. I played with the sliders, and decided I really liked the saturation boosted way up. I pushed various sliders around and decided I was ready to lock in the pixel values, and turn the 32-bit HDR into an 8-Bit (LDR) TIFF to bring back into Photoshop for final image adjustments. Under Image>Adjustments>Hue/Saturation, I added +35 Saturation, and then under Image>Adjustments>Curves, I added an S-Curve to increase contrast. A quick UnSharp Mask, and I'd made an image that looked much better than any of the original Low Dynamic Range photos. (See below)