The first problem leads to most RAW processing programs continuing to think that they’re processing a color file and, accordingly, preform demosaicking, which leads to resolution decreases, moiré, and aliasing. In the case of a camera converted to monochrome, equally exposed pixels that originally, before conversion, belonged to different channels, receive different RAW data numbers. In many cameras, sensor data is processed differently for different color channels before the RAW is recorded (for example, White Balance preconditioning for Nikon: the values of the red and blue pixels are multiplied by small coefficient).
The monochrome file recorded by the camera cannot be told apart from a color shot without a complete analysis of of the RAW data – all of the metadata corresponds to the color file. However, during such conversion, the firmware of the camera doesn’t change, and the camera doesn’t know that it’s become monochrome, which leads to the following: This, in turn, leads to higher resolution and a decrease in the number of processing artefacts (see the Bayer Moiré article), which is, essentially, why people perform the conversions of color cameras to monochrome. Since a color camera differs from a BW camera due to the existence of color filter array (CFA, Bayer mosaics) over the sensor, converting a color camera to BW is done by removing the CFA*.Īfter the CFA is removed, the demosaicking process that is done during RAW file processing becomes unnecessary. Nevertheless, there is demand for BW (Black and White) cameras (for reasons explained in detail below), and many photographers want BW cameras with the same lens mount as their main (color) camera, so that they can use the lenses they already own. 
Several Leica and PhaseOne models are rare exceptions, but these cameras are even more of a niche product than the color cameras or digital backs made by those same companies. Almost all digital cameras that are released today are color cameras.
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