In my fairly early years of photography, I got caught with the ETTR bug. Is that a fatal virus? Nope. ETTR is an acronym which stands for Expose To The Right. This ideology is based on the idea that a bright exposure with a histogram pushed as for towards the right (brightness side of histo) is the path to maximum image quality in long run. When exposing to the right, a user wants to make sure the highlights are not clipped or blown out of gamut. Lost highlights can’t be recovered much, there are no x’s and o’s on your memory card for your camera or computer to look at. On the flip side, having a slight overexposure of your shadow areas DOES bring in extra information in the pixels.
The above illustration hopefully shows how I “season to taste” on a landscape photo that I took yesterday. Setting the black level and white level can be a matter of personal preference, there are no hard-set rules. I like my pictures to tell a believable tale by retaining the integrity of the scene but I also want plenty of contrast so that my upload or print will “pop”. For this particular photo I used the Curves tool to bring the dark areas from a medium tonality to a darker tonality. This provides greater separation between the highlights, midtones, and shadows. I’ve also added a slight vignette which helped to “burn in” some bright corners from the original photo.

Optimized image, originally exposed to the right. Taken with my Tamron 18-270mm VC Lens and my Canon EOS M 18.0 MP Compact Systems Camera. Manfrotto tripod used for stability and a 3-stop Neutral Density filter was used to lengthen exposure time.
Finalized photo is above. A landscape nature frame taken in Pennsylvania. The equipment used includes a Tamron 18-270mm VC Lens, a Canon EOS M Camera, a 3-stop Neutral Density Filter, and a Manfrotto Tripod. Metadata: 2.5s F/13 ISO 100, 27mm in Manual Mode.