Pure Linear RAW Conversion

The term linear conversion has become the norm for describing pure RAW conversion. We don't see the need for this type of conversion in everyday photographic situations, but every RAW converter nevertheless has to be able to perform it internally.

A linear conversion converts the manufacturer/camera-specific RAW image data into RGB pixel data and alters the white balance and EV (Exposure Value) settings if necessary.

The result of a linear conversion is usually a very dark-looking image (figure 5-4), but this is the way all(!) interpolated RAW images look when the Bayer pattern has just been demosaiced.

In order to make such an image usable (figure 5-6), a tone curve like the one shown in figure 5-5 is applied. This is not the type of curve you would apply under normal circumstances, but it is the right one to use here. Such a curve can be adjusted to suit individual cameras and situations, but the basic form remains the same.

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