Values, an essential aspect

"The first things to study are form and values. For me, these are the things that are the basics of what is serious in art."

Jean Baptiste Corot (1796-1875), French painter

Value - An element of art that refers to luminance or luminosity — the lightness or darkness of a color. This is important in any polychromaticimage, but it can be more apparent when an image is monochromatic, as in many drawings, woodcuts, lithographs, and photographs. This is commonly the case in much sculpture and architecture too.

Tone and tonality - A quality of a color, arising from its saturation (purity and impurity), intensity (brilliance and dimness), luminosity (brightness and dullness), and temperature (warm and cool); or to create such a quality in a color. To tone down is to make a color less vivid, harsh, or violent; moderate. To tone up is to make one become brighter or more vigorous. Tonality can refer to the general effect in painting of light, color, and shade, or the relative range of these qualities in color schemes.

From this link.

I am going to do a new exercise with this photo:
the first way is to identify the values so I have edited the photo in black and white.