Grouping values
Link the darks into one shape. Link the lights into one shape. Let a mid value hold them apart. Confetti values read as noise; grouped values read as a picture.
A scene has hundreds of separate light and dark patches. A picture has three or four. The difference is grouping: you deliberately join adjacent darks into one continuous shape (the tree, its cast shadow and the dark foreground become one), join adjacent lights into another (sky and the lit field and the pale distance), and keep a halftone between them so they do not touch everywhere. Values scattered evenly across the page, like confetti, read as noise however accurately they are drawn.
Corot's calm comes from this. His foreground trees, their shadows and the near ground are one dark; his sky and distance are one light. Cotman designed a castle as three interlocking flat shapes before he drew a moulding. Squint at either and the grouping is obvious.
To group, you will have to lie a little: darken a halftone that interrupts your dark shape, lighten a dark that breaks your light shape. That is not cheating. That is composing.
Visuals
Cotman, Liber Studiorum: Plate 29, Harlech Castle, N. Wales, 1838. softground etching, from a bound volume containing 48 plates.
Cotman, Liber Studiorum: Harlech Castle. Squint. The castle, its rock and its shadow are one dark; the sky and water are one light; a halftone shore holds them apart.
The Cleveland Museum of Art · Bequest of John Bonebrake
Pitfalls
What
Faithfully recording every small light inside the dark mass.
Why
The dark shape breaks up and the design dissolves.
Fix
Keep at most one or two lights inside a dark mass, and only near the focal point.