Graphics Programs Reference
In-Depth Information
products do allow custom ICC profiles to be created to describe the final
RGB color space after a conversion from the RAW data.
Most digital SLR (DSLR) camera systems are intended to be used in
the field and do not interface with a host computer for rendering an
image. Most DSLR cameras give the user a choice in what kind of data
they want—processed predefined RGB color files, or the RAW sensor
Grayscale data file. The RAW can be converted into a full color image by
any number of software products after image capture. Out in the field,
most DSLR users simply want to capture their images, perhaps preview
the image on the camera's LCD, and move on. In most DSLR cameras,
there are several user-configured settings, usually called color matrixes ,
which instruct the camera how to render the original RAW data into a
preset processed color space if the user decides they want the conversions
to be handled by the camera. The choices are usually sRGB or Adobe
RGB (1998).
Many manufacturers provide as many as three to four flavors of sRGB
rendering to select for these conversions from the original RAW data.
Usually the different settings will produce different renderings from the
RAW data and encoded into sRGB, but with certain processing bias, like
more or less saturation. In a way, this is conceptually similar to how pho-
tographers have selected certain film emulsions from various manufac-
turers for certain shooting situations based on how that film renders
colors. No digital camera can initially produce either color space but
hopefully the RGB data rendered from the RAW capture is close enough
so that if a user assigns either sRGB or Adobe RGB (1998) to the result-
ing images, the image appearance will be reasonability pleasing.
The problem is, sometimes this is the case and sometimes it's not,
based on how well the manufacturer rendered the color. The other
problem is that the photographer is totally at the mercy of the camera
itself and how it was programmed to render the color appearance from
the RAW data. If, for example, the white balance setting on the camera
is incorrect, the color rendered from the RAW conversion will likely be
poor. The data is rendered and the original RAW data usually is deleted
so the final color appearance is fixed. That means editing, usually in an
8-bit per color JPEG document. With a RAW file, the color rendering is
defined when the user decides how to handle the conversion from RAW
to whatever color space and color appearance he or she wishes (output-
referred).
Virtually all RAW data is high-bit, meaning not only is the color
appearance customizable, the resulting RGB data can contain more than
8-bits per color. In fact, a RAW file is so flexible that white balance set-
tings on the camera play no role in the subsequent conversions. With
RAW and the right tools, you can control the rendering from one extreme
(scene-referred) to the other (output-referred). The only factor that
affects the RAW data is the ISO set on the camera and, of course,
exposure. RAW files, in many cases, have as much as one stop of addi-
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