Picture 1. A digital camera has saved the upper photo as a JPEG file and the lower photo as a raw file. Photos haven't been processed at all. The raw photo is clearly sharper.
Picture 2. An example of a digitally processed raw photograph. Here you can read about the process in detail.
The upper photo is the original unprocessed photo which has been saved as a raw file. The lower photo is processed in Adobe Camera Raw. The great color depth of the raw file provides excellent possibilities for post processing.
23.11.2007 Category: Photography
Digital SLR cameras and many bridge cameras can save photo as a raw file. Raw file is the unprocessed photo that the sensor of the camera captures. Raw image file includes the original saved data. Raw isn't a file format but it refers to several different file formats. Each camera manufacturer (for example Nikon, Canon, Olympus) have it's own raw image file format. For example the file extension of the raw file of Canon EOS 400D is CR2.
There are several image file formats that are used in digital cameras for saving photos. Here I'll compare raw format to JPEG format which is the most common file format for a photograph.
JPEG photo is always compressed so that some of the photo's original information has been lost. Raw photos don't have compression or they have lossless compression. (compression of raw files of some camera manufacturers is slightly lossy). By saving the photo as a raw file one can save all the data that the camera captured.
A raw file contains multiple times the amount of colors that a JPEG file does:
A JPEG file has 8 bits of color depth for each color channel (R G B). It means that a primary color (R G B) can have 256 (28) different intensity values. Mixing of primary colors leads to 16.8 (256x256x256) million different colors.
A raw file has usually 12 or 14 bits of color depth for each color channel (R G B). 12 bit color depth means that a primary color (R G B) can have 4096 (212) different intensity values. Mixing of primary colors leads to 68.7 (4096x4096x4096) billion different colors.
What is the use for more intensity values then? If the photo isn't processed, 8 bit and 12 bit photo could look pretty much the same. On the other hand if the photo digitally processed, the color depth has a great meaning. Because of great color depth the raw file provides very flexible processing possibilities. If you want to know more about the technical details I recommend reading more about raw files and color depth here.
Digital cameras usually process taken photos for example by adjusting sharpness, contrast and saturation. The changes that camera makes to JPEG file are irreversible. However, changes made to a raw file can be cancelled without loosing any image information. The greater color depth provides better image processing capabilities also other ways.
The file size of a raw file is many times the file size of a JPEG file. For example a 10 megapixel photo as a high quality JPEG file consumes about 2-3 megabytes of disk space on an average. A 10 megapixel photo as a raw file (CR2) consumes about 11-12 megabytes of disk space on an average. So a raw file can consume 5-6 times the amount of disk space that a JPEG file does.
A raw file is a lot slower to save and to modify than a JPEG file. That is because of the large file size and the great color depth of the raw format. The slowness of raw processing can transpire in several occasions:
Adobe Camera Raw is a Photoshop plug-in that works in Photoshop and in Bridge. Camera Raw plug-in is used to open image files that are in a raw format. Camera Raw is included in Adobe Photoshop CS3.
Another way to open raw files is to use Adobe Photoshop Lightroom which is a software created clearly for photographers.
A raw image file is suitable for those who digitally process photos and want the best possible quality. On the other hand JPEG image file is suitable for those who don't process their photos and want a file which is directly suitable for example for Internet, email attachment or print.