File formats vary widely; they include lossy compression types such as JPEG and JPEG2000, lossless compression types (LZW, ZIP, most RAW file formats), and uncompressed types such as standard TIFFs. For images destined for the web, use JPEG. For printing, uncompressed TIFF is often preferred, although high quality JPEGs are usually visually indistinguishable from TIFFs and may be preferred by some because of file delivery 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 that there are some caveats with 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.)
RGB master files should be left unsharpened or sharpened only on a removable layer, since resizing for future uses is likely. Master files should be archived along with the RAW files for a project.
RAW File Format: Although you should capture images in the best quality that your workflow requires, the best quality clearly comes from using the RAW file format. The advantages of RAW file format are:
The RAW file issue: While UPDIG advocates shooting RAW format files whenever your workflow supports it, there are several potentially negative issues with RAW file format as opposed to shooting JPEG or TIFF. Most serious is the issue of proprietary, undocumented RAW file formats becoming obsolete, unsupported, and eventually inaccessible. (A good analysis of this problem is found at the Luminous Landscape site.) In addition, there are workflow problems associated with RAW file formats. Proprietary RAW files need to be converted to another format, or must be 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 the ability to be non-destructively edited. If they are paired to sidecar files, they are harder to manage, and no cataloging software can read the information contained in the sidecar files. Even to proof-print 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 ways that this problem may eventually be resolved.
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 to the fact 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; nearly 70% of photographers say they always, usually or sometimes use it. One of the reasons is that it is unique in its 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 can be extracted 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 an all-in-one solution, 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 is yet to be seen; it will depend on how they develop and how universally they are adopted.