Seeing Black and White

In his book Seeing Black and White, Alan Gilchrist sets out to explore and explain the connections between light and human visual perception. As a whole, the human visual system remains a mystery because of unexplainable discrepancies; “the overall pattern of errors is the signature of the human software.” (Gilchrist, 2006) Throughout this book, Gilchrist recounts historical developments of light perception, examines the main theoretical perspectives, and shares his personal theories based on years of research. Gilchrist does not provide the exact science behind the human visual system. Instead, he juxtaposes the various research and theories while noting the strengths and weaknesses of each. This creates a strong foundation for understanding to nurture further discoveries.

Before Gilchrist begins unravelling this tangled web, he emphasizes the importance of understanding some key terms: Distal Stimulus, Proximal Stimulus, and Percept. Distal Stimulus refers to the object or environment itself with no regard to the viewer and his perceptions. Proximal Stimulus is the state of light reflecting from the object or environment to the eyes, producing an image. Finally, Percept relates to the human’s perceptions of the appearance. Gilchrist also makes an important differentiation between the terms lightness and brightness as they are often confused or considered the same. Lightness is perceived reflectance; a surface reflects a % of the light it receives – this is reflectance. On the other hand, brightness is perceived luminance; luminance is the amount of light reflected by a surface into the eye, a product of both reflectance and illumination intensity.

Gilchrist also sets the records straight for the misused term contrast. As he described three various uses for the term contrast, one seemed to tie in well with the element of tone. In class, tone was loosely defined as grays and neutrals. “Contrast often refers merely to the ratio (sometimes difference) between the luminance on one side of an edge (or gradient) and the luminance on the other side.” (Gilchrist, 2006) The role light plays in our ability to see so many tones expands the original “grays and neutrals” definition much further. Also, it seems to me that because contrast results from the ratio of light, our perceptions of an object’s tone can vary based on its surroundings; tone is contextual.

I always knew that the human’s visual system was unique, but I was unaware of the significant impact light had on our perceptions. Though I experienced several “what did I just read?” moments in the introduction of Seeing Black and White, I still found the information fascinating. Gilchrist really does write for the laymen to ensure clear understanding. Because of this effort, I would be interested in finishing his book. Even with the minor increase of visual perception knowledge I now have thanks to Gilchrist, I see the world around me differently.

Gilchrist, A. (2006). Seeing Black and White. Retrieved from http://site.ebrary.com/lib/lwtclearningcommons/Doc?=id=10160536&ppg=12