The \"expose to the right\" proponents advocate pushing exposure so the lightest tone in the scene is reproduced just below clipping to maximize the fact that digital captures more data points and tonal granulation (even gradients) in the brightest tones. So if the darkest tone in the scene is a medium gray, the ETR practitioner would intentionally overexpose it and make if off white in the camera capture, then edit it back down to its normal tone in Photoshop. The risk I see in doing that is the fact most scenes contain specular highlights and subtle highlight detail around those specular highlights which are critical for creating the perceptual illusion of 3D in a 3D photo. Overexposing middle-tones \"to the right\" will blow out the that subtle detail.
What the \"white towel\" method assumes is that even a black cat on a coal pile will have highlight details such as the specular reflections in the fur which define its 3D shape which are critical. The towel is just an easier to visualize proxy for those highlights. My goal is to preserve that detail even if it sacrifices shadow detail because in most full range image shadow detail is not critical to delivering the message. In fact too much shadow detail can be counter-productive if it distracts from the primary center of interest.
The way many people use HDR is a similar case of fascination with technology trumping perceptual and compositional commonsense. By putting more detail out of shadows than would be perceived by eye an HDR photo creates the same perceptual sea of sameness as flat lighting. HDR used effectively compensates for the limited range of the sensor, just pulling out the 3-4 stops of shadow detail the highly adaptive eye sees in person but the 7-stop camera sensor can\'t capture. When HDR starts to show more detail that seen by eye it starts to seem fake. That\'s useful for some creative purposes, but doesn\'t create a realistic facsimile of reality.
In the mid-80s one of our USIA magazines did a feature on Ansel Adam\'s work and I got to make the dual-black duotones from about a dozen of his more famous originals. Having read and applied his technical books and his read his biography I think the real genius in Adams work was his understanding of the role of human perception, with all its quirks, in the reproduction process. He realized how the eye adapted to the brighter parts of a scene, very much like a digital in auto mode, causing a loss of perception of shadow detail. The eyes have a finite dynamic range too. So when people looked at his photo of Half Dome and other iconic sights they would see in his prints more detail in the shadows than by eye. Adams had a fine sense of balance so there is not so much detail that the photo looked fake.
Being smart and lazy I can also appreciate that the zone system was born because Adams shared those same traits. Its more fun to take photos than make prints in the darkroom. The zone system is based around all prints being made the same way: #2 paper, exposed so film base +fog = maximum black the paper could produce with the least amount of exposure. If one exposed and developed the negative to fit the range of the #2, making the prints became pretty much a no-brainer and a job which could be delegated to assistants. Using the overexposure warning on the camera to correctly expose a digital file to the highlight detail is a similar \"no-brainer\" solution to a process some seem to find complex and throw increasing levels of technology at. Unless there is a new quantum leap in sensor technology I don\'t see sensor range ever matching that of an outdoor scene, so learning who to use fill flash so its not really obvious fill flash was used is a useful skill too
