U umetnosti, količina svetlosti u nekoj boji naziva se VALER pa, prema tome, pojam valerska skala označava isto što i pojam tonska skala svetla.
http://www.crtanje-i-slike.com/tonska-skala-svetla.html


Colour Glossary of Art Terms
- Colour value
The lightness or darkness of a colour; low value is dark; high value is bright.
http://www.visual-arts-cork.com/colour-art-glossary.htm


Tone, Value, & Texture
- Color is defined by its hue, chroma and tonal value. Tonal value is the lightness and darkness of a color, and it's this value we have to acknowledge and constantly assess when making monochromatic and achromatic drawings.


- Color, Value and Hue
Value is defined as the relative lightness or darkness of a color. It is an important tool for the designer/artist, in the way that it defines form and creates spatial illusions. Contrast of value separates objects in space, while gradation of value suggests mass and contour of a contiguous surface. In the drawing on the right, value contrast separates the artichoke from the background, and the separate leaves from one another, while gradation suggests the curves of leave surfaces and of the whole form.
http://char.txa.cornell.edu/language/element/color/color.htm