Once in a while one may want to adjust L channel viewing it separately. The rub is that to do this without using extra layers one needs either to use grey Lstar profile as grey working space in Photoshop Color Settings (Cmd/Ctrl-K), or to switch on Show Channels in Color in Photoshop Interface Preferences (Cmd/Ctrl-K). Otherwise the brightness and contrast of the L channel display are wrong.

With the existing diversity of RAW converters and their algorithms, there is the problem of choice: which converters are better (and for which purposes). An evident methodology is often encountered in internet forums: take one or several images, process them using different converters/algorithms/settings and compare them visually. The result often looks like this: image P should better be processed using algorithm Q, and image A is better handled by algorithm Z with option f+.

Moreover, it is simply wrong to analyze things in terms “worse or better”. The correct formulation is “closer to/farther from the initial image”.

The problem is that here we deal with a complex system, which includes

1. The photographed object and light.
2. The light path in the camera with lens aberrations and light scattering within the camera.
3. The sensor with all construction features: anti-alias filter, color bayer filters, microlenses, etc.
4. In-camera processing, both analog and digital.
5. And, yes, also the RAW converter in question.

The current methods used to determine the sensitivity of digital cameras are not based on the RAW data coming from the sensor; rather they are based on the results of processing the RAW in a converter (be it an external converter or in-camera).

This approach, with all its simplicity, is in fact based on the properties of the RAW converter and on the transformations it applies to RAW data. In particular, the converter can introduce hidden exposure compensation, change the tone curve, and so on. The sensitivity of the camera resulting from such a procedure is a pretty arbitrary value. The matter is discussed in good detail in Wikipedia, in the article explaining ISO 12232 standard.

This approach allows the camera manufacturers to enjoy all sorts of tricks while stating the sensitivity, say cameras from different manufacturers but having the same rated sensitivity behave wildly different when it comes to photographic latitude. This means that switching between different camera bodies one often needs to re-adapt, changing the way he applies exposure compensation.

A simple experiment that takes no additional equipment other than already existing camera and lens allows to accurately determine how the camera exposes, that is:

• which level of signal (in terms of RAW data) is obtained while setting the exposure by the exposure meter;
• what headroom in highlights is left, i.e. how many exposure stops are between the middle gray and sensor saturation.

The question that needs an answer is, for what purpose is the module designed. I can think of four different approaches to acquisition.

1. I want the module to do nothing more than open the file without damage. I understand that it will probably be flat and colorless if I do this. I intend to fix the problems in Photoshop.
2. Although I will refine the image in Photoshop, I would like to be able to make quick, obvious moves in the acquisition module to make life easier later.
3. I am not interested in the very best quality. I will do whatever is possible in the raw module but I will not work in Photoshop afterward. So I would like to be able to get attractive color from the module.
4. I want to make the image as perfect as possible in the module. I will intervene later in Photoshop only as necessary.

You need to decide which group(s) you appeal to.