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.
Let’s keep this good and widespread analogy to describe the next stage of digital photo image generation : « developing » the « negative film » (inside the « dark room ») to obtain the actual photo.
Raw files have to be converted to TIFF or JPEG standard formats similar to how negative films need to be developed to get the prints.
This is usually done by camera’s built-in software immediately after the image was captured and consists of applying various color corrections and file compressions considered by the manufacturer as optimal and by most users as satisfactory but this allows only little control of the user over the « development » process.
For professionals however, such approach might be simply insufficient as they might require full control over processing to determine the final appearance of the image.
Therefore, they would instead use more performant software , and hardware to achieve this.
Just for example, they can control brightness, contrast, gamma, sharpening, temperature adjustment (white-balance), noise reduction, tint, etc. not to mention file-saving formats and compression options.
To summarize : raw formats files contain all image data and information allowing later processing (« development ») up to highest levels of image quality or customization.
One can store a photo as a raw file then, based on it, create an infinity of versions of that picture using « dark room software », either existing or yet to come!
Alternately, camera software have limited processing performance compared to dedicated third-party specialized software, it outputs lossy or lossless images in formats such as JPEG or TIFF but everything is based on a range of settings among which only some are contrallable by user.
This option advantages amateur users as it is fast, painless and the quality is within, if not even beyond, their expectations.
We should not finish this article without mentioning Adobe’s efforts to introduce a standarizaton model for raw formats : they’ve created an openly documented file format named « DNG » (stands for Digital Negative), not very widely adopted, at least not yet.
But of course, our software, supports DNG format, as well.