QBARS - v35n4 Recording the Blues

W. George Waters
Reprint from Pacific Horticulture

In the spring 1980 issue of Pacific Horticulture there is an illustration of the clear blue flowers of Lechenaultia biloba . The photograph from which the illustration is made is on Ektachrome film, exposed without filter. It had no special treatment during preparation and printing and reproduces the color of the flowers well. There would be no need to comment on this correspondence of flower and photograph were it not that many photographs of blue flowers are disappointing. General statements about the inability of color film to reproduce the blues in flowers, although often heard, are unjustified, as our illustration of lechenaultia shows.
Why then, are some blue flowers well reproduced on color film and others poorly so? Manufacturers do not claim that their films reproduce color accurately, despite advertisements that imply otherwise. There is a constant search for dyes that will bring films closer to the color sensitivity of human vision, but discrepancies remain between what is seen and its rendering on color film, whatever the subject. Results from color photography are nevertheless pleasing and deviation in color, if noticed, is usually acceptable. It is the loss of good blue in some flower photographs that gardeners find hard to accept.
The color change most often complained of is the conversion of blue, or near blue, to purple from additions of red where none is seen in the flower itself. (The reverse change, from purple to blue, is seldom noticed.) Photographs of some lavender flowers show a similar degradation which renders them pink in photographs, and purple flowers are sometimes magenta, but these changes are less often complained of. When, as frequently happens, red flowers appear in photographs to be richer and more vivid than in life, the result may even be welcomed.
These color changes in photographs are usually the result of the same effect; the sensitivity of photographic film to infra-red rays. Infrared rays have wave-lengths close to those of visible red, but are just beyond the range of human eyes. They are difficult to separate from visible red in the film and affect it as though they were visible red.
The petals of some flowers absorb infra-red rays, others reflect them. Therein lies the difference between blue flowers that photograph well and those that don't. Petals that reflect infra-red rays, along with visible rays, onto the film, tend to have exaggerated redness or, in blue flowers, a purple cast. Those that absorb infra-red rays are usually well rendered on film.
Sky-blue flowers of morning glory are among the greatest temptations for color photographers, but their color is seldom captured. Himalayan blue poppy on the other hand, is capable of yielding good photographs as are some gentians. Most blue and near-blue irises suffer color degradation on film, but Iris munzii , a rare native of southern California, has flowers of a more brilliant blue than other irises and its color reproduces well on film. Some other irises native to the Pacific Coast have flashes of well-rendered blue on petals that are otherwise poorly reproduced on color film.
A filter over the camera lens can be used to stop infra-red rays, but is not popular. The filter, a pack of several elements, reduces effective film speed significantly. Need for infrared correction cannot be anticipated and success with the filter requires experiment with each subject. Information about the filter can be had from Eastman Kodak and their dealers. Simple pale blue filters are used by some to enhance the rendering of blue flowers. These filters also distort the colors of parts of the plant that are not blue and their value in improving accuracy of color rendering is limited.
Photography indoors, using light from flash guns or other sources matched to the film, avoids defects from the sun's infra-red rays. Photographs of blue, near-blue and lavender flowers taken outdoors on an overcast day are likely to give better results than those taken on a clear day, because clouds absorb much of the sun's infra-red radiation.