Creating an HDR Image with the Appropriate Software

The current version of Cinepaint is available only for Linux and Mac OS (http:// www.cinepaint.org/docs/download.html). So far, there isn't a version available for Windows. The same can be said about Krita. Therefore, for this example I will be using the FDRTools freeware version 2.3.2 that is available for Windows, Linux, and Mac OS to create HDR images.

Step 1: Loading the Bracketed Exposures—the Default Settings

After you start FDRTools Basic, several windows open, as shown in figure 3.119.

The upper-left window, FDRTools Basic, is used for opening and editing the images. Top right is the toolbox with the eyedropper. It is used for the (manual) white balance. Underneath that is the Progress window with its progress bars for the individual procedures of the tool. The Navigator window at the lower left basically shows what happens when applying a setting. Here you can toggle between the HDR Image Inspector and the Tone Mapped Image tabs. The HDR Image Inspector shows the HDR image with the current settings applied, whereas the Tone Mapped Image view shows the actual result for output.

Clicking the + One button opens the Open Images window. Select the images you would like to work on. In this case, you should open the RAW files (NEF files) on the DVD in the Exposure Bracketing subfolder of the SampleImages folder. Select the images and click the Open button.

Figure 3.119

The windows of FDRTools at startup. The upper-left window is the main window.

Figure 3.119

The windows of FDRTools at startup. The upper-left window is the main window.

U SI NG MASKS AN D LAYERS—PAI N TI NG, FI LLI N G, AND COLOR TOOLS

After the pictures are imported, the main FDRTools window will display the opened files. The program creates a new project. On the left next to the preview images you will find three buttons: Prepare, Edit, and Render.

Click Prepare. The program prepares the images for further editing, as you will see in the progress bar in the Progress window. The preparation takes some time, but in the long run it saves time.

Figure 3.120

The main window with the opened and already aligned images. The Navigator is depicting the HDR image, corresponding to the actual settings.

Step 2: Automatic Alignment

After the Prepare function has finished processing, click the Edit button. The main window changes its appearance. Again the program processes the images automatically and aligns them to each other. The HDR Image Inspector at the bottom displays the first preview of the merged HDR image.

A small green box next to the Include button indicates that all three images have been linked together. This means that the HDR image will be processed with all the tagged images. You can take out or add an image simply by clicking on the Include button.

Figure 3.120

The main window with the opened and already aligned images. The Navigator is depicting the HDR image, corresponding to the actual settings.

Step 3: Creating the HDR Image

The next step is to create the HDR image. Click the HDRI Creation button in the main window.

In the program window, the histogram showing the default values for the HDR image opens. You also see the histogram for each individual image. You can choose between two buttons, Auto and Exif. Auto processes the image using the image data from the program. Exif processes the image according to the attached Exif files that have been attached by the camera. In this example, however, only Auto is active.

In the histogram to the right of each of the preview images, you can apply gradation curves. Slide the dots on the lines by selecting them with the mouse. You can also apply new dots by clicking on the curve with the mouse. A click on the Defaults button resets the settings to the default values.

By default, the HDR Image Inspector tab in the Navigator window is initially active. You can switch to the Tone Mapped Image tab to view the brightness and color rendering in the finished LDR image.

When the HDR Image Inspector tab is active, you can click the Auto button. This option allows you to adapt the rendition of your image automatically to the settings of your monitor. Next to it you will find a slider that corresponds to the big histogram of the HDR image in the main window. With it you can readjust the brightness of the HDR image.

The actual customization of the image for the exercise will take place in the following step: Tone Mapping (the second button from the right at the top of the main window).

Figure 3.121

The program window after clicking the HDRI Creation button.

Figure 3.121

The program window after clicking the HDRI Creation button.

Figure 3.122

Tone mapping in FDRTools using the Simplex method

Figure 3.122

Tone mapping in FDRTools using the Simplex method

Step 4: Tone Mapping to Adapt the Rendition to the Monitor and Printer

In order to attain an optimal rendition of an HDR image file on the monitor and printer that matches their capabilities for rendering contrast ranges brightness and color, you must carry out a tone mapping procedure. Thus you generate a file that defines the selected settings and features in a way in which the image can be saved and reproduced on the monitor and the printer.

Select the Tone Mapping feature by clicking on the button in the main window of the FDRTools program. A histogram appears in the main window, as depicted in figure 3.122.

A new tab opens up in the main window: Simplex. It offers a simplified method of tone mapping.

Under Postprocessing you can see a processed histogram of the image. The window offers the possibility to edit gradation curves, brightness, contrast, and colors in the image. This function relates to what you have already seen in GIMP'S Colors > Curves (section 2.5.9). By moving the Saturation slider under the histogram, you can define the intensity of the colors.

Now the Tone Mapped Image tab is active in the Navigator window. The image in the Navigator is a preview according to the settings in the main window.

3.15 GIMP AND HDR

If you are satisfied with the rendering, you can save the image by clicking Save in the main window.

You also have the option of a second tone mapping method. Click on the Receptor tab next to Simplex in the main window.

In the Receptor dialog box, you have several tone mapping options to choose from. The value on the Compression slider defines the strength of the tonal range compression. A higher dynamic range (color and brightness contrasts) exacts a stronger compression. FDRTools recommends using values between 1 and 5 for RAW images (the program allows you to use the tool for individual RAW photos) and higher values up to 10 for HDR bracketed exposures.

The values shown here were set according to the result visible in the Navigator's preview image. The result after saving can be used to check if the image is rendered too bright or too dark. If necessary, you can make corrections using GIMP. You can edit the image by applying a tonality correction or the gradation curves to quickly reach the desired result.

As soon as you have optimized the image, click Save in the main window.

The Save Tone Mapped Image window opens; it resembles the standard Save as window. Select where you want to save your image, give the image a name, and choose the file type for the image. You can choose between 16 bits/channel and 8 bits/channel color depth, depending on if you want to save your HDR image in high quality or use it for further editing in GIMP.

Figure 3.123

The setting options of the Receptor tone mapping method.

Figure 3.123

The setting options of the Receptor tone mapping method.

CHAPTER 3

U SI NG MASKS AN D LAYERS—PAI N TI NG, FI LLI N G, AND COLOR TOOLS

Now click the Save button. A new window opens: Save LDRImage. In this window you can see the entries for the LDR image. By default, these are saved as PNG files. This is an image file format you can continue editing in GIMP.

Figure 3.124

The Save LDR Image window after location, file name, and file type have been selected

Figure 3.124

The Save LDR Image window after location, file name, and file type have been selected

On the bottom of the Save LDR Image window, you can check the box Open LDR image with check box and then click Browse to select the program in which you want to open your LDR image after it has been processed.

Now the Save button is active. Click it to process the image. This can take some time.

The processed image opens in GIMP with the settings shown in figure 3.124. You might be asked if the image should be opened with the embedded color profile or if the standard color profile should be applied. If in doubt, select the standard color profile. A tonality correction in GIMP will lead to a final and hopefully desired result.

Try it. The picture should be quite impressive. Compare it to the reference image hdr-reference.jpg in the SampleImages folder on the DVD. It is astounding what you can retrieve from backlit photographs using this method or the alternative GIMP method.

3.15 GIMP AND HDR

One more note on FDRTools: After you have exported the LDR image, the process is completed. It is not intended to save the image as an HDR file. Nevertheless, when you shut down the program, the project is saved with all edits and adjustments that you have made. So you may reopen the project and alter the settings to your convenience.

Figure 3.125

fdrtools_hdr.png

Figure 3.125

fdrtools_hdr.png

We come to the end of this chapter on the topic of working with layers and masks. So far, we have been working with color photographs. Naturally, the methods I've demonstrated can also be applied to black-and-white photographs. What you have to watch out for in black-and-white photography will be discussed in the next chapter.

Naturally, GIMP is not limited to color representation. You can also edit black-and-white photos with GIMP. In addition to the functions and tools used when editing color images, the program offers specific tools for modifying black-and-white images. What's more, you can use GIMP to colorize old black-and-white photos.

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