Painting and drawing, from life, heighten perception, as both require observation. However, the act of drawing seems to augment the sense more. This could be due to the nature of the medium, and time spent preparing to apply the marks.
Even with a familiar pigment layout on the palette, time is still needed to identify and mix every colour observed. The majority of drawing materials, such as pen, are ready for immediate application. More space is thus allotted to concentrating on the subject in question. Despite the cross hatching technique used in this drawing, ink on paper, I was able to observe each object more than in a painting. Drawing is always stressed as an important companion to learning.
Painting of course heightens the perception of colour. However, colours exist more in relation to other colours. A tint is bright if a darker hue is nearby. Only drawing forces a study of individual things.