ABSTRACT

Dumb black and white conversions When you change a color image in Photoshop from RGB to Grayscale mode, the tonal values of the three RGB channels are averaged out to produce a smooth continuous tone grayscale. The formula for this conversion blends 60% of the green channel with 30% of the red and 10% of the blue. The rigidity of this color to mono conversion limits the scope for obtaining the best grayscale conversion from a scanned color original (see Figure 5.1). The same thing is true if you make a Lab mode conversion, delete the a and b channels and convert the image to grayscale mode, or if you were to simply desaturate the image. There is nothing necessarily wrong with any of these methods, but none allow you to make full use of the information that’s contained in a color image.