RAW vs JPG File Formats
Beyond the shared goal of storing information about a picture the RAW and JPG formats have nearly nothing in common. One stores information in a standardized format, the other differs between cameras. One creates smaller, compressed files that have had information removed. The other creates huge files that maintain every detail. The easiest way to explore these differences is to walk through the photographic process from the click of the shutter to the final digital edit.
As soon as light hits the camera's sensor the image format you have chosen begins to affect the final result. If the image is to be stored in JPG format, then the camera has a lot of work to do. Your camera's sensor will provide between 12 and 14 data points (bits) for each pixel of the image but the JPG format can only store 8 bits of information for each pixel.
In order to figure out the best possible value for each of these precious bits, a number of factors must be taken into account. Your settings for white-balance, contrast and compression will all have an impact. Any information that falls outside the range represented by your presets is lost. The JPG format will also drop some detail in order to reduce file size. The result of all this processing is a standardized file that is not overly bulky and can be viewed and manipulated by nearly any photo editing software on the market.
When shooting in RAW mode, things happen differently. The camera will not attempt to interpret the data from the sensor. It will record all the original values for each pixel without sacrificing any information. White-balance, contrast and other important information is stored as a notation about the data, but will not affect the actual image. With a RAW formated image, the shutter speed, ISO setting and aperture are all that will have an impact on what is recorded.
The exact format used to store the image data will vary between vendors. Even two cameras from the same vendor may use different versions of the RAW format. Some will compress the data, others will not. Regardless of the specifics, the shear volume of information being stored will result in a file that is significantly larger than an equivalent JPG image. In addition to requiring extra storage space, the RAW image will also take longer to write to the memory card.
When you connect your camera to the computer you will see another consequence of your file format choice. While there is a nearly endless supply of programs that support the JPG format, the number that can edit the exact version of the RAW format used by your camera will not be as high. The camera vendor will supply one solution. In addition to the software supplied by the vendor, Adobe's Photoshop is likely to support your camera. The current version of Photoshop (CS3) supports over 150 different RAW formats.
This format profusion and reliance on vendor specific software is often sited as one of the drawbacks to using the RAW format. Adobe is working to solve this problem – even for those who don't use Photoshop.
The company has created an open standard for the RAW format called the Digital Negative or DNG for short. This open standard is already being at least partially adopted by several major vendors including Hasselblad, Rioch and Samsung. Until more vendors standardize, Adobe offers a free utility for download from their website that will convert proprietary images into DNG format. This version of the RAW format has much wider software support than the individual proprietary implementations. Unlike a conversion to JPG, converting an image from a camera's native RAW format to the open DNG standard does not result in data loss.
Once inside the editor, the advantages of using RAW start to become clear. You will find you have far greater control over the details of the image. Tonal information that would be deeply embedded in a JPG image can be easily adjusted. Even changing the entire color space used by the image possess no particular difficulty.
Also, using this single high quality original you have the option of producing copies targeted to different purposes. It is easy to produce high quality TIFF images, or even create JPG images of a higher caliber than what your camera could produce. Lighting can be adjusted to create multiple versions of an image suited to different media and uses.
It could be argued that not every shot needs to be retouched in exacting detail and that for these instances RAW is a waste of storage space and time. Given ever falling memory prices, the storage space issue is quickly resolving its self. As for post processing, while RAW does allow you significantly greater control over individual images, this does not mean you have to use it every time.
By taking advantage of batch processing in your photo editor of choice, you can easily create JPG copies of all your images using either the camera's original settings, or your own. Since your computer's processing power far exceeds that of even the most high end cameras, the resulting images may look better even without retouching. If at some future date, you decide you are not happy with the JPG results, you will still be able to go back to the original RAW file. Taking the few extra seconds on each image will pay off when you don't have to spend hours making adjustments to that crucial shot that could have been done in seconds using a RAW original.
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