UPDIG Photographers Guidelines | version 4.0
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File Formats
File formats vary widely. They include "lossless" compression types, such as LZW-compressed GIF and TIFF, PSD and most raw file formats, and uncompressed types, such as standard TIFFs. Some formats, such as JPEG2000 and HD Photo (JPEG XR), offer both lossy and lossless compressions. Although lossy compression at high compression rates can create visible artifacts, many call lower compression rates "visually lossless." For the web, use JPEG. For printing, uncompressed TIFF is often preferred, although high-quality JPEGs are usually visually indistinguishable from TIFFs, and some prefer them due to file delivery and/or storage considerations.

Between capture and final output is an important intermediate step: the RGB master file. RGB master files are Photoshop (.PSD) or TIFF files, optimized in a large-gamut color space, such as Adobe RGB or ProPhoto RGB, at either the digital camera's native file size or interpolated to a larger size (consistent with any possible future use) by a raw-file-conversion program.

(We should mention there are some caveats to consider when choosing an extra-wide gamut space such as ProPhoto RGB instead of Adobe RGB. While the larger gamut does imply a wider range of image data preserved "down the line," it also implies bigger image transformations, possibly with bigger shifts in the color of the image, when it is converted to a narrow-gamut color space such as CMYK. In addition, an extra-wide color space necessitates the use of 16-bit image editing to avoid problems such as posterization or banding.)

Leave RGB master files unsharpened or sharpen only on a removable layer, since resizing for future uses is likely. Archive master files along with the raw files for a project.

raw file formats
Although you should capture images at the highest quality your workflow requires, the best quality clearly comes from capturing in a raw file format. The advantages of raw file formats include:
  • The photographer can choose a different color space each time the file is processed.
  • The file offers greater bit depth.
  • The file captures the maximum dynamic range.
  • The processing operation can adjust white balance, saturation, exposure (to a degree), tonal characteristics, highlight recovery, noise reduction and lens corrections, all in a non-destructive way.
  • Many raw processors have sizing algorithms some say are superior to interpolation in Photoshop, since they are working with the actual pixel data captured by the camera's imaging sensor.
  • You can process raw files in a variety of software, from the camera maker's own tools to many third-party products, and even the built-in raw processing of Apple and Windows operating systems.
the raw file issue
While UPDIG advocates capturing raw format images whenever your workflow supports it, there are several potentially negative issues with raw file formats as opposed to capturing JPEGs or TIFFs. Most serious is the issue of proprietary, undocumented raw file formats becoming obsolete, unsupported, and eventually, inaccessible. (Luminous Landscape offers good analysis of this problem.) In addition, there are workflow problems associated with raw file formats. Proprietary raw files must be converted to another format or paired to sidecar files, before metadata can be safely added. If the raw files are converted to a standard format, such as TIFF or JPEG, they lose their ability to be non-destructively edited. If they are paired to sidecar files, they are harder to manage. And no cataloging software can read any color adjustment information contained in the sidecar files. Even proof-printing raw files, so your client can see your intended interpretation of the file, usually requires a batch conversion to another file format. There are several interesting possibilities for solving this problem:
  • OpenRAW: The OpenRAW organization hopes to persuade camera makers to provide open documentation of their proprietary raw formats. Open documentation would improve the archiving outlook. At the same time, it would enhance the ability of third-party developers to create better raw file processors and more timely support for new cameras and their raw formats.
  • DNG (Digital Negative): Another approach is Adobe's open-architecture DNG file format. While Adobe characterizes DNG as an openly documented format, some people have objected that it can contain undocumented information, such as camera-maker notes, and can even contain encrypted data. Others object that it is not universally accepted and can be used by only a few kinds of software or cameras. DNG, however has several important positive features. According to the OpenRAW survey, Adobe Camera Raw has more than twice as many users as the closest competition. One reason is DNG's unique ability to combine the functionality of a standard raw file with the capability of safely accepting metadata. In addition, a DNG file can contain a full-size, color-corrected JPEG that is visible to cataloging software. These JPEGs can be used to make prints, or they can be copied and delivered to clients as high resolution files. And, although it makes for a large file to archive, a DNG file can contain the original proprietary raw file, which can be extracted and processed anew at a later time.
  • New raw file handling software: Competing with the camera vendors' software, Adobe's Bridge/Adobe Camera Raw, and such stand-alone applications as Bibble, Nikon's Capture NX and Phase One's Capture One are new types of "raw file handling" software. Examples include Apple's Aperture and Adobe's Lightroom. These applications aim to be all-in-one solutions, handling everything from start to finish: ingesting files, browsing and selecting, rating, adding metadata annotations, cropping and image editing, printing, creating slide shows, and cataloging. Whether they prove to be indispensable tools will depend on how they develop and how universally they are adopted.
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