Use this layer to control all of the tonal qualities of the image.
For the first time in a coloured RGB file, the operation of RGB Curves and Levels can now be accurate. Both Curves and the Levels RGB interface can be used meaningfully. Now tonal editing is almost a luxurious pastime.
Unique qualities of this Layer:
When you think of tonality control in digital imaging you think first of Curves, and then you may include Levels or some other tools. But Curves is definitely the first choice for any tonal control.
Yet, in the argument introduced in “Experiments in Curves”, the potential accuracy of the RGB interface in Curves is not realized in a regular RGB file of greater than zero saturation.
If we recognize digital imaging as the most important element of contemporary photography, why are we not using the most important tool accurately?
The Luminosity layer enables extremely accurate use of Curves that makes it a joy to use and this is achieved while you remain in RGB mode.
This accuracy and meaningful feedback makes an Adjustment Curves layer on the Luminosity layer the first step in editing many files. Control points and lockdown points can be made quickly and they work directly with the pixel you have chosen.
This accuracy and feedback is extended to the use of the Levels and the Levels histogram.
We are often led to believe that this accuracy is always the case in a regular Photoshop file but it is not!
Most texts misrepresent the nature of Curves and Levels please read the Lobster manual and dispute its independent research!
The Luminosity layer is also a great site for any sharpening and blurring, dodging and burning operations It is efficient and does not cause any change in Hue from any operations.
The Luminosity layer can be nominated as a target in Apply Image which means that qualities of files in any forms may be nominated as tonal qualities and can be applied to an image if the other file has the same pixel dimensions and bit depth as the Luminosity layer. This extends to files in some other modes.
What is the Chromaticity Layer?