The proper lighting of a color photograph is something we often think about only after we place a photograph on the wall and find that it doesn’t look quite as good as we thought it would. Even the best print cannot overcome the limitations imposed by the incorrect color or intensity of light.
We often forget that what we are actually viewing when we see a print is the light reflected from it’s surface. This reflected light determines, to a large extent, the appearance of the image. If you try to view a print at night in a dark room, nothing is visible—or if you view the print only with a red light bulb, all you see is red and shades of black.
These examples are extreme but the principle fully applies to situations we commonly ignore, especially fluorescent lighting or the generally low light levels present along many interior walls. Color prints are significantly more sensitive than black and white prints to a change in the color or intensity of the viewing light. Why is this?
A large proportion of the important information in a color photograph is, of course, about color: color which changes hue, saturation, and brightness with the color and intensity of the viewing light. Black and white prints consist almost entirely of shades of grey, with very little visual information which shifts with various kinds of viewing light.
Our perception of black and white is a visually processed sensation. That is, under normal daytime viewing conditions there are no sensors for white, black or grey in the eye. Our sensation of black and white is actually a continually shifting standard that compensates for the color and intensity of the viewing light. This works fine for black and white photographs, but our perception of color has a more limited compensatory mechanism.
The color and intensity of light may change, but due to the complexity of our visual mechanism, we tend to not see those differences in light quality. However, our perception of many saturated colors does change, because the actual signal levels of the color sensors in the eye change. Our eyes incorrectly tell us that the viewing conditions have changed only moderately while the print appears to have changed significantly. Of course, the print does not change at all — only our perception of it has changed.
We are only aware of a small portion of these changes in the viewing conditions — but the colors of the photograph seem diminished and it appears to be darker and with reduced luminosity and brilliance. Not a desirable result! How can we avoid this and light the print so that it may be viewed in the best way?
First of all, it is important to realize that fluorescent lights, while appearing to be fairly smooth and neutral white, actually contains a number of spikes of light in narrow spectral bands which lead to significant errors in the viewing of certain colors. Fluorescent lighting results in “jagged” color harmonics, the distortion of relative values of colors, and the visual loss of many delicate colors with close values. This directly relates to the non-continuous spectrum of fluorescent lighting and the attendant peaks and valleys of light intensity across the visible spectrum. Additionally, many people find the not quite sub-threshold flickering of these lights to be disturbing.
Incandescent lighting has a visual spectrum which is smooth and continuous. However, incandescent lights always have more energy in the red and yellow end of the spectrum and it is especially important to avoid bulbs which have been rated at 130 volts, as these will give an overall orange cast. The best lights for viewing prints are incandescent halogen lights, as these lights have filaments which burn hotter in an inert (halogen) gas, and thus give more light toward the blue end of the spectrum than conventional bulbs.
I recommend halogen floodlights of 50 to 75 watts. The lighting fixtures should be about 30° to 45° from the print, placed in such a manner as to eliminate reflections from the glass into the viewer’s eyes. If your fixtures are more than four feet from the print, you may need the blending of two lights to achieve this. A uniform overall brilliance without harsh ‘hot-spots’ is the goal. Generally, floods are better than spots, but if the lights are over 6’ from the print, two spots may be necessary. If a light intensity meter is available, the light on the prints should read between 55 and 75 footcandles, the higher amount for predominately darker images.
If we think of the print as the performance of an image, it is easy to supply the proper lighting conditions to insure a “command performance.” It’s worth the effort to get it right!