All DSLRs and many recent highly-featured digicams support two capture formats: JPEG or Raw. TIFF may also be offered. Raw is quite different from the other two formats in several ways:
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All DSLRs and many recent highly-featured digicams support two capture formats: JPEG or Raw. TIFF may also be offered. Raw is quite different from the other two formats in several ways: 1. It has not been subjected to in-camera processing (hence it is in a ‘raw’ state) 2. Each Raw file format is proprietary, which means different camera manufacturers have different Raw files. The format can also differ for different cameras within a manufacturer’s line-up. 3. Special ‘decoding’ software is required to open Raw files. Again, this differs from one manufacturer to another. 4. Raw files must be converted into TIFF or JPEG format before they can be edited or used in any computer-based application. In contrast, both JPEG and TIFF files are created after the image data has been processed by the camera. Each camera manufacturer has its own processing strategies (and algorithms) and some image processors are definitely better than others. JPEG also compresses image files by discarding image data that is unlikely to be missed by normal human vision. In the process, images can become degraded. What’s in a Raw File? When you shoot a Raw image, the resulting file contains the raster data, the pixel coordinates and colour channel information from the sensor that defines the image, along with metadata indicating the camera’s exposure, white balance and sharpness settings and how this data can be used when the file is processed on a computer. It also contains information that allows the computer – where the final processing of all Raw files takes place – to open the file. Photographers can use this data to ‘tweak’ image files so that when they are converted into TIFF or JPEG format, the image is as close to their original ‘vision’ of the subject as possible. Many photographers also use the image metadata in the file to help them with this ‘tweaking’ because they can view the camera’s settings and adjust parameters accordingly. Because the metadata in a Raw file is complex, and the processing is carried out on a computer, the processing is much more sophisticated than in-camera processing. Photographers who use Raw can also:
Conversion Issues Because camera manufacturers create their own proprietary Raw formats, cameras capable of Raw capture must be supplied with decoding software. This can range from highly-automated amateur converters that provide few adjustments, to powerful applications that provide full control over the conversion. Converters are frequently specific to one or two camera models. They can also vary between relatively efficient and agonisingly slow. Some manufacturers charge extra for more capable RAW converters but most bundle them free of charge. Converters are usually updated with each generation of new cameras. As more cameras include Raw capture, manufacturers are beginning to supply software developers with ‘kits’ or APIs (application programming interfaces) that allow them to decode the camera’s processing algorithms and provide a standard interface for an image editing application. Adobe’s Camera Raw is a typical example. Where the API isn’t provided quickly enough, some (generally smaller) software developers ‘reverse engineer’ camera makers’ Raw file formats and create their own decoders. However, these decoders often have limited functionality. Their sole objective is to unlock the Raw file so photographers can view and edit the image. Consequently, many totally ignore the metadata, which remains inaccessible. Photographers who wish to use the metadata when converting Raw files should avoid such applications. Even bundled Raw file converters have limitations. Some restrict photographers’ abilities to specify the bit depth for each image, change colour space settings and control how and where the converted image file is stored. Some provide a wider range of adjustments than others, while a few lack batch processing capabilities. Towards Uniformity? Currently there are well over 100 different Raw file formats in existence. However, many of these relate to discontinued cameras and are no longer supported by manufacturers. This means photographers with older Raw files can only open them with the software that was supplied with the camera used to take them. If that software is lost, the files may become inaccessible. Concern about this issue led Adobe to develop a ‘universal’ Raw file format, known as Digital Negative (DNG). DNG is actually an extension of TIFF, the longest-lasting, most widely-accepted bitmap format. Its specifications are published on Adobe’s website for anyone who wants to develop, market or distribute hardware and software that reads or writes DNG image files. However, although DNG can handle all current known variations in camera sensor design, it is only designed as a standardised way to store different Raw file formats. While it may make thumbnail images more accessible, it is unlikely to be an effective substitute for the manufacturer- and model-specific processing that is needed for the most flexible and effective conversion of a Raw original to TIFF or JPEG format. Platform Support On 1 June, 2005, Microsoft joined forces with leading camera manufacturers, Canon, Fujifilm and Nikon, to announce a modular software platform for handling Raw files. This platform will be part of Microsoft’s next-generation imaging engine (code named ‘Avalon’) and form the basis for a soon-to-be-released Microsoft RAW Image Thumbnailer and Viewer for Windows XP, which will allow users to view thumbnails and preview and print Canon and Nikon RAW files from Windows Explorer in Windows XP. The camera manufacturers involved have collaborated with Microsoft to ensure the power of proprietary Raw file conversion programs can be replicated with native support in the Windows OS. Microsoft is developing a certification program to give third-party hardware and software manufacturers an image-processing software ‘codec’ (code and decoder) specific to their Raw format to ensure they work with its operating systems. The next version of Windows (known as ‘Longhorn’) will also provide an API that enables software vendors to exercise more control over the Raw conversion in their applications. It will also support professional-level conversion tools. Photographers will benefit by being able to work with Raw image files just as easily as with JPEGs today. They will also have more choices as new camera models are introduced because the plug-in architecture should allow them to upgrade their image-editing software when they upgrade their hardware by simply loading a codec plug-in supplied with the new camera. Image Archiving Microsoft’s initiative will also have advantages for photographers who use Raw as an archiving format – which an increasing number of photographers are now doing. Just as you can produce multiple prints from a single negative, you may also want to create multiple, different files from a Raw image file. With the way Raw file converters and editing software is evolving, it is possible that the images you’ll be able to generate from your Raw files in the future will be superior to the images you can create today. Photographers who have archived images as Raw files should be able to take advantage of such improvements – provided camera manufacturers continue to support older Raw file formats in the future, even if that support is provided mainly through the user’s operating system. This is one reason why Microsoft’s announcement is so important. Your Choices If you wish to work in Raw and use it for archiving your images, how your equipment handles Raw files will be important. When evaluating a new camera you should take account of the following criteria: 1. If you prefer using the manufacturer’s Raw file decoder to a third-party application, how effective is the software supplied with the camera? Does the converter provide all the controls you need? Can you decide where you will store converted files? How much can you adjust key settings like exposure, white balance, contrast and sharpness? Does it support 16-bit TIFF conversion? How long does it take to process each Raw file? Are batch processing options available? The importance of these parameters will vary for different photographers but we think they are all important enough for every new camera buyer to consider them before making a purchase. 2. How widely is the Raw file format supported? (You can tell how effectively camera manufacturers are working with software developers by the speed with which applications are updated to include new camera models.) 3. How long will the Raw files produced by the camera you buy today be supported? If you use Raw files for archiving, this may be the most critical issue of all. Some Cautions Raw is not an appropriate format for anyone who takes a casual approach to photography. A good understanding of the nature of the adjustments provided by the file conversion program is required to use them productively. Converting Raw files into TIFF or JPEG format is also time-consuming, so capturing in JPEG format is preferable for photographers who need their images in a hurry. Consider a Raw file as the digital equivalent to a photographic negative, and the processing software as an analogue of the darkroom practices used to produce the picture from that negative. Competence – and knowledge of the physical and chemical processes involved in making a silver halide print – were the keys to creating great images from originals shot on film. Though the technology may have changed radically, the requirement for competence and understanding of processes is still the key to successful digital prints.
Links for more information on the RAW debate and raw files in general:
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