Scotopic Photo Topic

Debate about the application of color in photography will continue as long as there are photographs. Feature articles on the topic pop up with great regularity in the standard photo mags, and online articles and debates rage endlessly. My local bookstore carries at least two magazines, B&W and Black and White Photography, dedicated entirely to one camp (and yes, Benetton's advertising rag Colors, too).

The language of these debates is often laughably inflammatory, raging from "anyone shooting B&W today is morally suspect" to "B/W is the true photographer's medium." It's right up there with declarations like "film is dead" (and has been for many years, or so I've often been told in one well-meaning lecture after another since at least the early 90's) or "digital is just craftsmanship, photography [with silver wet processes] is art."

Can somebody open a window in here? Phew!

There have been both monochrome and colored images since the days of cave painting. Raphael and Durer worked in both. This long history suggests to me that both kinds of image have merits that are embedded deeply in human development and the way our brains function.

While it's common knowledge that humans have greater color discrimination than, say, cats or dogs, color vision is evolutionarily very old — and probably developed for the sake of identifying food. At a very primitive level, animals can identify organic compounds by simply filtering UV — more recently, our tree-dwelling ancestors used complex color vision to identify which berries were sweetest (the "L" photoreceptors in our eyes, which detect red, are a late evolutionary addition). Color vision also plays a role in sexual selection and community wellbeing, providing animals (especially furless ones like humans) quick reference to the health and potential fecundity of available mates.

Advertisers have recognized the appeal of food and sex for a long time, and it was the desire for color advertising that drove color printing into magazines and then newspapers. It's hard to competetively market mac & cheese or lipstick without color, if your competitors are using it. And nothing sells cars or liquor like a pretty, clear-skinned girl.

Our eyes, unlike our cameras and printing presses, have two overlapping vision systems. We have scotopic vision, provided by the rod cells (which don't distinguish color but work well in low light) and photopic vision provided by cone cells (which show color but need a lot of light). The centers of our eyes (the fovea) are dominated by color cells, but the eye as a whole is heavily dominated by monochrome rods.

Significantly, our eyes don't only have two different classes of cells for detecting colored or panchromatic light — those different cells are actually wired-into the optic nerves and the brain in very different ways. The monochromatic rods pass their signals to the visual cortex quickly, with a minimum of filtering. This is to be expected for quick response, since the rods dominate our peripheral vision and are key to our ability to navigate through the world and react to objects (read: predators) approaching from the sides.

Color cells connect in groups to local processing cells, comparing the inputs of the various red, green, and blue-sensitive cones. These processors then route their information further, to cells near the center of the eye, which process yet further and only then pass their information upstream to the cortex. Their inputs are more-considered, but also slower. The red and green cells are sometimes confused, resulting in variations and color blindness — the blue cells are scattered less-frequently, and shift in focus and apparent detail against red and green (useful to designers for creating some dimensional effects in art, such as the notion that reds pull "forward" from the page, while blues "recede").

The more we look at human color vision, the more we realize that it varies considerably from what occurs in CCDs or color films.

In short, what many accept so readily as "real" from color photography is every bit as much an abstraction as what we see in B&W. Not only that, but our brains actually experience the two kinds of images in different ways, and at different speeds; along different neural pathways; and with different primordial connections. Both kinds of vision have function, both have their own character. And barring injury to our brains and eyes, we're stuck with both kinds of images, as long as we and our audiences remain human.

To borrow from Matthew Alpern: "the real business of primate vision is the discrimination of features or objects based on their location; color vision is just a hobby."

Comments on "Scotopic Photo Topic"

Jon Fernquest
July 25, 2003 05:32 AM

Thanks for the clear and concise biological explanation of why both B&W and color are essential. I've always felt that but couldn't articulate any reason why.

September 15, 2003 04:15 PM

this is just great. I love this photo.


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