RAW format files; TIFF; DNG; NEF; CR2; CRW and others
RAW files are image files compiled directly from the raw data collected at the Digital Image Sensor of the camera or other image file creating device (scanners etc). The data is retained unprocessed and none of the data is discarded. The file formats differ as do the identifying metadata tags.
RAW files store the raw data from the camera. That data is then used in post production to produce the image required by the photographer. Once the image is produced using an editing application the another format is output as the final image file. An example of a processed image file would be a .jpg (JPEG) or PNG file or one of a range of other formats. Thus, RAW files tend to be intermediate file formats used for storage and transmission and for resourcing post processing.
RAW images are sometimes referred to as digital negatives and one particular format is actually called .DNG (Digital Negative – by Adobe Systems). The DNG format was produced by Adobe to create an open standard for RAW files. Although a number of camera manufacturers have taken up the option, both Canon and Nikon have not committed to the format. They have so far stayed with their own formats…
- Canon RAW: .CR2 and formally .CRW
- Nikon Electronic Format: .NEF
There are a whole range of other RAW formats. Many of the proprietary brands are linked to camera or scanner manufacturers. The Tagged Image File Format (TIFF) is one of the best known. The specification dates from the 1980s and was formally published in 1992. It has proved to be a robust and successful format. TIFF was intended as a digital scanner/archive format and as such is still used for that purpose today. It provides a popular format for photographers and other image professions. It supports high colour depth (16 bit colour depth) and a multi-image format too. Originally the format was created by Aldus, a company in scanner and desktop publishing. However, today Adobe also own this format having purchased Aldus. Today, TIFF and DNG are probably the most well known archive formats as well as robust contenders for a digital negative standard. The file structure and coding is well established for both and openly published so future generations will be able to decode the files for both. Adobe Systems, the company who owns the copyright to both, are open to discussion for development and appear to encourage uptake by manufacturers as they have issued open licenses for both formats.
Conversely, Canon and Nikon have not published specifications for their respective RAW formats. These proprietary RAW brands remain under full control of the manufacturers. As a result, some applications may not immediately be able to use the format without code libraries supplied under license by Canon or Nikon respectively.
The TIFF is a flexible bitmap image format supported by most image-editing, desk-top publishing, scanners, painting and illustration applications. Also, virtually all desktop scanners can produce TIFF images. The TIFF format uses the .tif extension. The format supports the main colour-space formats including CMYK, RGB, and grayscale and alpha channels as well as a range of other colour types. The format also supports both Lossy and Lossless compression types.
The advantages and disadvantages of RAW as an image file and an output format from the camera
|High image quality.||Large file sizes.|
|No in-camera processing||Processing is time-consuming|
|All image data retained; none discarded||Demands intense computer resources|
|Editing changes do not change the base data||Applications have to use alternative file formats as output (eg. *.jpg)|
|Fine control of all aspects of exposure, brightness, colour and contrast||Requires highly developed image editing applications|
|Editing changes can be re-changed later||N/A|
|Lost detail in very dark areas/very bright areas can be recovered||N/A|
|Can only use lossless compression without file damage||Compression ratios unpredictable – some files still very large|
|File created with all data||File creating is time intensive; shot burst numbers reduced|
|File created/stored in-camera with all data and metadata||Large files file the on-camera memory card|
|Proprietary RAW formats = good camera hardware/software compatibility||Large number of specialized software codecs required in applications|
|RAW is a good storage/archive format||Lack of published proprietary standards – bad for archiving as future interpretation may be limited|
|Photographer has full control and processing discretion||Much skill and training need for full professional advantage of RAW|
|Professional skills in processing provide quality and artistic images||Expensive and lengthy fine art training often required|