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Real World Camera Raw with Adobe Photoshop CS4: Using Adobe DNG Converter

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Adobe DNG Converted is a convenient way to process large numbers of images into DNG format. Bruce Fraser and Jeff Schewe show you how.
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Adobe DNG Converter is a simple application. It’s not the only way to convert proprietary raws to DNG—you can save DNGs right out of Camera Raw—but it’s a convenient way to process large numbers of images into DNG format. See Figure 3-8.

The main screen lets you set the following options:

  • You can choose a source folder full of raw images for conversion, and optionally include subfolders.
  • You can choose a destination, either in the same location as the source raw files or in a new folder, with the option to preserve the subfolder organization.
  • You can rename the converted images with the same options as the Batch Rename command in Photoshop and Bridge.
  • If you have previously saved DNG files with the original raw file embedded, you can extract the original raw file.

To change the conversion options, click the Preferences button to open the Preferences screen—see Figure 3-9.

The conversion options are likewise very straightforward:

  • Preview allows you to select the size of the embedded DNG preview or to turn previews off.
  • Compression (lossless) applies lossless conversion. Unless you own stock in a hard drive vendor, we can’t think of a reason to turn this off. And yes, the compression is truly lossless.
  • Preserve Raw Image preserves the raw pixel data in its original mosaic format. Use this option if you want to be able to use all of Camera Raw’s features. You can convert a DNG saved this way to a linear DNG, but not vice versa.
  • Convert to Linear Image saves a demosaiced version of the image. This option is mostly useful if you want to use a DNG-compliant raw converter other than Camera Raw on images from a camera with a mosaic pattern that isn’t supported by the raw converter. Linear DNGs are much larger than mosaic-format ones, so if you’re thinking you can save processing time by converting to linear DNG, think again—any savings in processing time are offset by the extra time needed to read the data.
  • Embed Original Raw File embeds a bit-for-bit copy of the original raw file in the DNG, from which it can be extracted at any time. You can use this option for your archived images just in case you need to retrieve the original raw files at some future date, but we suggest you turn it off for your working files to save space, because embedding the original raw file increases the file size considerably.

When you click Convert, DNG Converter goes to work converting the selected raw files to DNG format using the options specified in Preferences, and displays a status window that shows the progress of the conversions—see Figure 3-10.

To extract the original raw files from DNGs with the original raw embedded, click Extract, which opens the Extract Originals dialog box. Here you can specify source and destination folders for the extraction. When you click Extract, DNG Converter extracts the original raw files from the DNGs. See Figure 3-11.

At the time of this writing, the main benefit offered by DNG is the elimination of sidecar files, and it’s entirely up to you whether you want to use it, though it’s easy to do so. There’s no particular urgency to adopting DNG, but if you care about the longevity of your images, we do recommend archiving at least one copy of each image in DNG format, and if you want to be able to retrieve the original raw files, embed the original raw in the DNG. That way, you’ve preserved the raw image in a format that’s documented and hence is likely to be readable as long as humans can still read.

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