Value & notan
Analyse the light–dark structure of a reference photo. Reduce it to greyscale, to two, three or more values, blur it as if squinting, and read the value of any point, then plan your own compositions as notan thumbnails.
Value before hue
Value is the lightness of a colour, independent of its hue (red, blue…) and its chroma (how intense it is). We read form, light direction and spatial depth almost entirely through value: a drawing with correct values and wrong colours still looks solid, but correct colours at wrong values look flat or confused. This is why a greyscale photo of a painting is such a strong test.
Hue is a poor guide to value. Saturated yellow is far lighter than saturated blue, and the swatches on the right are all different hues at the same value: turn them into greyscale and they become one grey.
Notan (濃淡, Japanese for “dark–light”) is the arrangement of light and dark shapes in a picture, independent of what they represent. Introduced to Western art teaching by Arthur Wesley Dow around 1900, it is used for small thumbnail studies that plan a composition in two or three flat values before any detail or colour is added.
Six hues, all at CIELAB L* 62 (value 6.6 on the 1–10 scale used below).
Value analyser
Load a reference photo (it stays on this device: nothing is uploaded) or use the sample still life. Choose a view, adjust the thresholds on the sliders or by dragging the handles on the histogram, and click or hover on the image to read a value.
Image
View
Thresholds (L*)
Squint
Layout
Greyscale is CIELAB L* computed from sRGB (Rec. 709 primaries, D65) relative luminance, shown as a neutral grey of the same luminance. Value on the 1–10 scale = 1 + 9 × L*/100 (1 black, 10 white). Large images are reduced to 1600 px on the long side for processing.
Using it for a study
The analyser is a check, not a tracing aid. Look first, commit to your own reading of the values, then compare.
- Compare notans, not detailsSet 2- or 3-value mode, then photograph your drawing and load it too. Differences in the big shapes (a dark mass too small, a light that leaks out) matter more than any edge or texture.
- Squint to see massesHalf-closing your eyes suppresses detail and local texture so only the large value shapes remain. The blur slider does the same; raise it until small marks disappear and judge the design from what survives.
- Keep the darks connectedScattered dark spots read as noise; linked darks form one strong shape that holds the picture together. If your notan breaks into islands, look for shadows and dark objects that can join up.
- Decide a value for each shapeBefore shading, assign every major shape to light, mid or dark and keep the groups separate: lights in shadow stay darker than darks in light. Set the thresholds so the key matches the families you intend to use.
Notan thumbnail sheet
An A4 sheet of empty frames for planning compositions by hand in three values. Work small and fast with a marker or soft pencil: white paper for light, hatching or a grey marker for mid, solid black for dark.
Frames
Aspect ratio
NOTAN THUMBNAILS
- Block in only the largest shapes: no outlines of detail, no gradients.
- Give every shape one of the three values in the key, and keep to three.
- Try several arrangements of the same subject; pick the one that reads clearly from across the room.