Opening and Developing a RAW Format or Digital Negative with GIMP

GIMP can open most but not all RAW file formats offered by camera manufacturers. As a start, you can use GIMP for editing these images directly, but only with a color depth of 24 bits (8 bits per channel). However, if you want to develop your digital negatives with the original color depth of 16 bits per channel (rather than 8 bits) in order to make fine-tuned corrections and/ or print a higher-quality photo, you'll have to depend on the RawPhoto or UFRaw plug-in. Once you've integrated one of these plug-ins into GIMP, it will automatically become active when you open a RAW file with GIMP. Let's first take a look at the UFRaw plug-in since it can be installed at a later point in time, as described in section 1.4.5.

UFRaw can be used in three different ways. If used as a GIMP plug-in, when you open a RAW file in GIMP, the UFRaw window will automatically open. You can set corrective options for color and brightness values in the preview window. This lets you develop and correct your image before even opening GIMP.

You can simply click OK on an open image to load it into GIMP. Then you can use GIMP's tools for corrections—a legitimate practice. However, the UFRaw program supports a color depth of 16 bits per color channel. This allows you to make detailed adjustments, whereas using GIMP's familiar tools limits the color depth to 8 bits/channel.

In addition, UFRaw can be used as a stand-alone program for developing digital negatives. During installation, the program creates a desktop icon or a Start menu entry on demand. With the UFRaw stand-alone, you can save images in the PPM, TIFF, and PNG file formats with 8-bit or 16-bit color depth per channel. The JPEG file format saves images at 8-bit color depth per channel. The example images in this section were produced with UFRaw stand-alone.

Moreover, UFRaw offers a batch mode (available for the Linux platform; to obtain information about this feature, enter man ufraw or ufraw—help in the Linux console).

The main UFRaw window is designed so that the various working commands are displayed in the sequence in which they will be applied to the image. You can open an image in UFRaw and experiment with the options to see how they affect your image.

Figure 2.1

An unedited digital negative was just opened in UFRaw's preview window. The left panes show color histograms and setting options.

Figure 2.1

An unedited digital negative was just opened in UFRaw's preview window. The left panes show color histograms and setting options.

2.2 OPENING AND DEvELOPING A RAW FORMAT, OR DIGITAL NEGATIvE, WITH GIMP

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In the following section, I will illustrate the development of a RAW image, a backlit photograph, and the necessary work steps for developing and editing the image with UFRaw before it's handed over to GIMP. Furthermore, I will introduce RawTherapee, a program resembling UFRaw for developing digital negatives yet with an additional range of functions and an ability to support a wider range of file formats.

Figure 2.2

The edited image with minor color corrections. Note that the left pane reveals the slight changes that were made on the curve to correct luminosity and on the slider to increase saturation.

Figure 2.2

The edited image with minor color corrections. Note that the left pane reveals the slight changes that were made on the curve to correct luminosity and on the slider to increase saturation.

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