Introduction to Medical Illustration PLME 0400

Drawing 4 Colors and Shades of gray Light and dark: Value Structure

• How does value relate to light and form?

Specular highlight (reflex)

Intermediate (halftone) Core dark Ambient shadow

Cast shadow Penumbra

Reflected light Value Structure

1. How does value relate to light and form (value structure: “how gray is it?”) 2. How does value relate to local color (Hue/Value/Chroma) Color • Three factors: – Hue: What color is it? (red, purple, magenta, green) – Chroma: How intense is the color (how green) – Value: How light or how dark is the color • Shade: color + black • Tint: color + white Color • Three factors: – Hue: color temperature –warm v. cold – Chroma is almost the same as saturation – Value is similar to grayscale: how dark is it? Color • Three factors: – Hue: color temperature –warm v. cold – Chroma is almost the same as saturation – Value is similar to grayscale: how dark is it? Color • Three factors: – Hue: color temperature –warm v. cold – Chroma is almost the same as saturation – Value is similar to grayscale: how dark is it? Light and dark: Value Structure

• When making a sketch: – Think about contrasts – Don’t be afraid to over‐emphasize – Practice “your 6 grays” – Equivalent to the value of colors? Color v. Grayscale • Not all colors are created equal • At its highest chroma (saturation), – Purple is the darkest color (highest value) – Yellow is the lightest color (lowest value) • A “really purply” purple is very dark • A “really yellowy” yellow is very light Color v. Grayscale • Not all colors are created equal – Doppler effect • Sound waves reflecting off moving objects change frequency • Shorter if object moves toward transducer • Longer if object moves away from transducer Color v. Grayscale • Not all colors are created equal – Doppler effect in ultrasound: Conventions • Blood flow is coming toward observer = artery = red • Blood flow going away from observer = vein = blue – However: Red and blue have different values Color v. Grayscale • Not all colors are created equal – Doppler effect in ultrasound: Conventions • Adding yellow/orange in one direction and (light) green and blue in the other compensates for the different values of natural red and blue Color v. Grayscale • Heat maps (over/underexpression of genes) – LEFT: green is brighter than red. – RIGHT: blue and red have the same value Color v. Grayscale • Heat maps (over/underexpression of genes) – When translated to gray scale, the lighter green contrasts with the darker red (L) Color is subjective Color is subjective A little color is great

No color hierarchy: What are we supposed to focus on?? 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Group 1Group 2 Drug A Drug B Drug C Drug D Drug E A little color is great

Emphasis on what happens with Drug A (red) 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Group 1Group 2 Drug A Drug B Drug C Drug D Drug E A little color is great

Emphasis on what happens with Drug A (red) 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Group 1Group 2 Drug A Drug B Drug C Drug D Drug E A little color is great

Emphasis on what happens with Drug E (blue) 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Group 1Group 2 Drug A Drug B Drug C Drug D Drug E A little color is great

• Use color schemes – Complementary colors • Primary (red, blue, yellow) • Secondary: combo of the other 2 (green, orange, purple) – Presence of one makes the other stand out A little color is great

• Use color themes – Notice the “odd one out” A little color is great

• Use color moods – Warm and cold colors

Frank Deng, Ann Int Med 2020 A little color is great

• Color conventions – Red cross – Blue mood – Green bile A little color is great

• Color conventions – Red = artery (but not always*) – Blue = vein (but not always*) – Yellow = nerve A little color is great

• Color conventions – Red = artery (but not always*) – Blue = vein (but not always*)

Artery: blood from the heart to the periphery – pulmonary artery brings

O2‐poor blood to the lungs

Vein: blood to from the periphery to

the heart – pulmonary vein brings O2‐ rich blood to the heart Arteries v. Veins

• Red v. blue?

Medical illustration

• Translate from color to grayscale Medical illustration

• Translate from color to grayscale Medical illustration

• Translate from color to grayscale In‐class exercise • Use grayscale to render organs and vessels