This week we will provide our general public with explanations on camera RAW files formats because this subject is often ignored or misunderstood and because our software supports more than 40 such formats.
Let’s start by specifying that “RAW“ is no accronym for anything : in this rare case, “raw” literally means “raw” (“unprocessed”, that is) and the explanation for this term resides in the way digital cameras work.
Each time you are taking a picture, you are actually exposing the digital camera’s photo-sensitive chip to light.
The chip has millions of sensor units (ie, pixels) each one translating the amount of light it was hit by into a voltage level which is then converted to a digital value.
Usually, this resulting digital value can be recorded in a 12 bits or 14 bits workspace, meaning that each pixel can handle 4096 brightness levels (= 2 ^12) or 16384 brightness levels (= 2 ^14).
Commonly, no sensor records colors : imaging chips record greyscales and then convert to color by using filters and color schemes such as the Bayer Matrix .
Finally, when saving a raw file, the camera software adds various metadata (information on camera type, camera settings, etc) but this information has no influence on the stored raw image, it is simply added as tags.
In other words, the raw image data is unprocessed and uncompressed and the various settings associated with it are not applied : they are stored as metadata for later use.
To conclude description of this stage of digital photo image generation in digital cameras, we should add that raw files have big sizes, their format is proprietary to the camera manufacturer (sometimes even specific to a certain camera model) and they are often compared to “negative photo films” from classic photography process.