Curves adjustments are one of the key tools in photo editing, and Lightroom offers three ways of making curves adjustments. What’s more, the curves tools look different in Lightroom CC and Lightroom Classic CC. Complicated? Not once it’s explained…
Luma curve
Most curves adjustments in photo editing are carried out on the image's RGB channels, either all together (to maintain the same color balance) or individually (to produce color shifts). RGB curve adjustments, however, produce changes to image saturation at the same time. Luma curve adjustments do not. Here, only the luma (luminance) values are altered, not the color values. As a result, with luma curve adjustments only the contrast is changed, not the saturation.