RAW file refer to the digital information, recorded by the sensor, before any interpretation are applied. Decoding a RAW file could be done with software included with the camera or with software designed to do this. Typical RAW file are usually larger than their equal .jpg files. Lossless compression reduces the size of RAW file. .jpg files use a lossy compression. This means that some data is loss by the .jpg files while all data is kept by the RAW file. RAW file store 12 to 14 bits per channel. This means that for the Red Value, up to 214 value of luminance is available. .jpg files allow for only 28 Luminance Value. These digits might not mean a lot to you but let’s do the math:
214 R X 214 G X 214 B = 14 Bits Raw File
This means that each pixel could have 4 398 046 511 104 different value. On a .jpg file
28 R X 28 G X 28 B = 8 bits .jpg File
This means that each of these pixels have only 16 777 216 different values. The difference could be considered AWESOME however there are some big caveats to this:
- No digital sensor today can record 14 bits of luminance value. The dynamic range of the most recent sensor is more in the range of 11 bits of luminance;
- There is compression in luminance at both end of the spectrum. Software fixes in cameras, this however illustrates the limits of current technology;
- These 11 bits of luminance are compress to 8 bits to create a .jpg in Camera. In fact, since no media today allow for printing or displaying 9 bits plus of information, these extra bits have very little use.
This being said, there are multiples advantages and more challenges associated with shooting RAW. On the plus side of RAW:
- More data is useful. Particularly in the darker areas where each bit of data means a greater changes. When working with the file to make it more pleasing to the eyes, .jpg with its lower luminance capabilities are showing their limitation quite fast and noise appears in the shadows;
- Some of the data might be outside of the Histogram, either on the bright side or the dark side. With RAW, if there is data outside you can bring this information in the visible windows of the 8 bits .jpg with special software;
- RAW files are read-only. This means that any software you use will let you make changes on the side for the sole purpose of output or exportation. This means protection for your originals compare to .jpg;
- With RAW file you can do HDR with a single file. The data available to you is only 11 bits but it does work to a certain extent!
- Changing setting like White Balance, Noise reduction and all other usual .jpg usual setting will be as good being done in post than on camera. This allow for some error margin.
On the minus side of RAW:
- Files are twice as big;
- You can post a RAW file to a web site without processing it;
- The number of shot allowed while shooting in burst will be less than with .jpg;
- Each files needs to be manipulated before being used.
Certain used clearly favor .jpg shooting. Sport, Action or any work where the files are urgently needed! Other used would favor RAW shooting. Landscape is clearly on the RAW side. Whatever you do, remember, shooting RAW allow you more flexibility in the future. .jpg is more what you shot is what you get!