Leadwort

What’s blooming in the area: Tamarix, tea roses, Apache plume, butterfly bush almost gone, trumpet creeper, Japanese honeysuckle, silver lace vine, leather leaved globemallow, alfalfa, white sweet and white prairie clovers, yellow evening primroses, datura, goats’ head, bouncing Bess, stickleaf, chamisa, winterfat, ragweed, snakeweed, native and farmer’s sunflowers, áñil del muerto, horseweed, wild lettuce, African marigolds, tahokia daisies, purple, heath, strap-leaf and hairy golden asters, pampas grass; canna buds, bittersweet berries; more Virginia creeper turning red.

What’s blooming in my yard, looking north: Zucchini, nasturtium, Mexican hat, chocolate flower, blanket flower, black-eyed Susan, chrysanthemum; leaves on butterfly weed turning yellow, catalpa leaves turning yellow and dropping, sand cherries turning red, seeds on blackberry lily.

Looking east: California poppy, hollyhock, winecup, snapdragons, Jupiter’s beard, large-leaved soapwort, Autumn Joy sedum, garlic chive, Maximilian sunflower; leaves on peony turning color.

Looking south: Rose of Sharon, sweet pea, Crimson Rambler morning glories, zinnia, cosmos; grapes turning red.

Looking west: Caryopteris, Russian sage, catmint, calamintha, David phlox, leadwort, purple ice plant, Silver King artemisia, purple coneflower, Mönch aster; leaves turning orange on skunkbush and white spurge; peach leaves turning yellow and dropping.

Bedding plants: Moss rose, sweet alyssum; edible tomatoes.

Inside: South African aptenia.

Animal sightings: Rabbit, geckos, bees, wasps, grasshoppers, large black harvester and small dark ants.

Weather: Short bursts of strong winds late some days; rain Thursday; 11:55 hours of daylight today.

Weekly update: Some flowers are definitely camera shy. Some weigh so little, they never stay still long enough for a camera to capture them. Others reflect so much light they blind the lens. The blues are trickiest of all, because their wiles defeat the camera itself, not just the photographer.

Of all the blue flowers in my garden, leadwort is the hardest to photograph. Early in the morning, when the Chinese natives are in shade, images look like they were taken underwater. By the time the sun reaches the west facing bed, the petals have begun to protect themselves by reflecting light. I was only able to get a clear picture last Sunday when the sky was still bright, but a little rain was falling. Even then the color was wrong.

Unlike the old silver-based film cameras, nothing is constant with a digital device. Then, if a picture was out of focus, the photographer knew he or she hadn’t set the distance parameter, the focal length, properly. With a computer-controlled camera, two parts of a plant the same distance from the lens, will appear in different degrees of detail. The reddish brackets that hold the pinkish tubes of the five-petaled leadwort flowers are always clear.

The same variation occurs with color. When the light is right, the leaves, the stems, the tubes and brackets are reasonably true, but not the petals. The reds, greens, browns and whites are fine. Only the blues are bad.

The chemicals in the plant absorb light both as part of photosynthesis and as the nature of matter. What we see is the light that’s not absorbed. In the case of leadwort, the flower is absorbing the yellow center of the visible light spectrum and ignoring the reds and blues, which the human eye combines into purple. On the other hand, the leaves are rejecting the green, and using the rest of the light to feed themselves

Jeffrey Harborne identified the flower pigment in Ceratostigma plumbaginoides as europinidin, a reddish blue anthocyanin derivative of the bluish purple delphinidin typically found in members of the plumbago family. Later this fall, when the leaves turn a burgundy red, the plant will have produced a cyandin monoside that will reflect light differently. Earlier, when they broke through the ground the second week of May, the new leaves were a shiny green.

Chemists themselves have troubles defining colors precisely. When William Lawrence’s team was testing the anthocyanin pigments in fall leaves, they found a number had one hue when seen in daylight and another when seen in artificial light. The nature of light is not constant from morning to noon, from clear to cloudy, from June to September.

Whenever I try to explain to myself what has happened with my pictures I get tangled in the differences between the reality of the physicist’s linear spectrum that fades into infrared at one end and to ultraviolet at the other, and the vocabulary of the artist’s color wheel which sees purple as the junction between red and blue. When I compare the photograph with the flower I see, it looks like the blue is bad because the red has been lost, only the blue has become lighter, not darker as a consequence.

I finally defined the two colors, the actual flower and its representation in the language of the computer monitor, which sees everything as a mix of red, green, and blue. The one is roughly 130 parts red to 50 parts green to 255 parts blue. The other is 100 parts red to 130 parts green to 245 parts blue. The first formula lacks the depth of the petals, but 255 is the maximum allowed for any color. The second doesn’t capture the sheen or white overtones of the photograph.

My camera uses the established technology that existed when it has introduced in 2005. The light enters through the lens to bounce against a prism that redirects it down to the CCD chip that converts the light into electronic impulses. Thom Hogan indicates such chips are more attuned to the high-energy infrared and somewhat blind to the low-energy blues. Some of the loss of blue, from 255 to 245, may be a consequence of that limitation; some of the loss of red (from 130 to 100) may come from the manufacturer’s attempt to compensate for the infrared sensitivity.

Computer chips only see on and off, which translate into black and white monochromes. The first stage of coloration comes from two layers of filters that sit above the CCD chip. One alternates red and green filters, the other blue and green so every point on the chip has one green filter and one of another color. At this point, the only loss of color comes from the quality of the filters.

The camera then takes the information from the chip and from the filters and combines them, using proprietary algorithms that try to reconstruct the relative importance of the data captured by the two layers. Since engineers know most people are more sensitive to green, than to red or blue, they tend to favor green when the pattern isn’t clear. And so, the amount of green in my picture is increased from 50 to 130, which distorts the flower color.

The variations increase when the image is transferred to a computer monitor or printer, because each piece of equipment has its own way of translating the RGB schema.

I originally asked questions about my camera’s technology so I would have some idea what features I needed if I replaced it. It never occurred to me to alter my garden so only the flowers that could be photographed would be allowed to grow. Nature is still more complex that it’s scientific representation, and flowers can be remembered without mechanical devices.

Leadwort is one of the last perennials to emerge in spring, rising in new places along the soaker hose where its rhizomatous roots have extended themselves. It’ll be one of the more colorful this fall. It’s now been putting out low flowers every few days since the middle of August. I grow it for the pleasures lived and those remembered, not for being recordable.

Notes: Charge-coupled devices (CCD’s) were developed in 1969 by Willard Boyle and George E. Smith at AT&T Bell Labs. The network of filters was patented by Bruce Bayer for Kodak in 1976. In the nineteenth century, Thomas Young and Hermann von Helmholtz established humans perceived colors from only three band widths of light; the existence of separate human receptors for red, green and blue (RGB) was finally established in 1983 by Herbert James Ambrose Dartnall, James K. Bowmaker, and John D. Mollon. What I call a part of color, using the language of artists, actually refers to the intensity of the light measured by the physicist.
Hogan, Thom. "How Digital Cameras Work," bythom website, last revised 9 April 2009, provides the clearest explanation for the layman.
Harborne, J. B. "Comparative Biochemistry of the Flavonoids-IV: Correlations Between Chemistry, Pollen Morphology and Systematics in the Family Plumbaginaceae, " Phytochemistry 6:1415-1428:1967.
Lawrence, William John Cooper, James Robert Price, Gertrude Maud Robinson, and Robert Robinson. "A Survey of Anthocyanins. V," Biochemistry 32:1661-1667:1938.
Photograph: Leadwort, taken around 3:30 on 20 September 2009.