Plugged In: Get light right when shooting and showing photos

By Joe Kashi, for the Redoubt Reporter

Nearly everyone has some favorite pictures or artwork hanging in their home or workplace. Most often, those pictures and artwork are not displayed to best advantage due to poor lighting.

Look around at nearly any good art gallery or other professional display space. The lighting of exhibited work is bright, simply done, aimed at whatever is being displayed, and has good color rendition. As a result, shadow area details are clearly visible and colors are correctly rendered and true to life.

Although I certainly believe in energy conservation, most “energy saving” light sources in current use are quite unsuited for lighting and displaying any sort of pictures and artwork, especially photographs. That’s particularly true for every type of florescent light and nearly all LED lights. Our eyes and brains are very good at seeing a wide range of lighting yet interpreting that light as being white. Artwork and photographs are not nearly as forgiving, mercilessly showing the effects of bad lighting through poor color rendition.

Without going too deeply into the physics of the matter, our eyes and brains have evolved and function best with natural daylight. Every rainbow shows us that natural sunshine has a continuous color spectrum in which there is a smooth distribution of light containing a mix of all colors of the visible spectrum. That continuous spectrum results in accurate color rendition.

In contrast, florescent and LED lights, even those that claim to be “daylight spectrum,” have an inherently discontinuous spectrum that actually uses only a few sharply delineated colors, mostly green. Such light sources rely on the human eye and brain to make florescent and LED light appear whiter and more neutral than it really is. Photographs and other artwork can’t be fooled. As an example, the neutral gray areas of even a well-made color print will have a greenish tinge when viewed under florescent light.

In many ways, digital photography eases our workload, at least about ensuring acceptable color balance. Traditional camera films were particularly sensitive to the overall color characteristics of the light in which they were used, with uncorrectable color errors when used with the wrong sort of light. In contrast, the auto color balance of a digital camera acts rather like the human eye and brain, reinterpreting the light actually recorded by a camera to make the final recorded result appear more nearly white and correct.

A good illustration of both how the “color” of light affects images and also of automatic digital correction would be to take some photos where the camera’s automatic correction is canceled out. First, make a few photos outside on a cloudy but well-lighted day with your camera set to “indoor” or “tungsten lighting” white balance. The photos will appear to be much too blue overall, with warmer colors like yellows and reds badly rendered, perhaps to the point of appearing dark or virtually gray.

Similarly, if you take some indoor photos under regular incandescent light bulbs while your camera is to “daylight,” “cloudy” or “shade” white balance settings, the indoor photos will appear yellow to brown. In this case, cooler colors like blues and some greens will suffer.

After this test, be sure to reset your camera to auto white balance. This two-minute exercise also shows why it makes sense to save your photo files in RAW format rather than solely in JPEG. Do this exercise saving all files in JPEG and then make a similar batch of photos, saving them in an RAW format.

Import the files into PhotoShop and try to correct the off-color images. It’s easy to correct RAW format images and to retrieve correct color balance because all color data recorded by the sensor is retained by a RAW file. That data can be correctly reinterpreted by later applying the right color balance setting in PhotoShop or other post-processing programs.

With a JPEG file, though, it’s virtually impossible to achieve a correct result for this test because the color balance is “baked” into a JPEG file and can’t be undone or reinterpreted. The additional color data needed to make the correction do this is no longer available — it’s discarded by the JPEG compression process and gone forever.

The color temperature rating of a light source (usually rated in degrees Kelvin or “K”) denotes the most dominant color in a continuous spectrum. Lights with a higher K rating tend toward bluish-appearing light while regular incandescent light bulbs put out a predominantly yellow-brown light and have a lower “K” rating. Most halogen bulbs are a bit less yellow than regular low-temperature incandescent bulbs, but only somewhat better.

Standard halogen spot and floodlights have a continuous spectrum but only a 2,900 K to 3,200 K color temperature. That does not render photos and other artwork properly. Still, they’re better than regular light bulbs. Natural sunlight has a color temperature, for art display purposes of somewhere between 5,000 K and 6,500 K, but at that color temperature, colors tend to appear somewhat too blue.

Generally, lights with a 3,500 K color temperature and a color rendering index of 95 or higher seem best for displaying photographs and other artwork. The closest match to true color and lighting are the SoLux type bulbs, a fairly new and patented light bulb for track lighting. Color temperatures are available from 3,500 K to 4,700 K. Most SoLux bulbs are designed to replace smaller twin-pin MR 16 bulbs used in the usual 12v track lighting, rather than in standard screw-in sockets. Some 120-volt screw-base SoLux bulbs remain available but are increasingly uncommon because they do not meet new energy conservation standards. The 12-volt MR16 bulbs and track heads do meet current energy efficiency requirements and thus are far more common.

While on the subject of lighting, portraits are one of the most common types of photography that require good lighting technique. Nationally prominent Texas photographer Kirk Tuck has posted a free online portraiture and lighting class that I highly recommend for everyone, including casual family photographers. You can find a link to Kirk’s class at http://visualsciencelab.blogspot.com/2013/11/my-free-portrait-course-has-been-live.html. His daily photo blog, www.visualsciencelab.blogspot.com, contains a wealth of insight and good advice, particularly about portraits.

Local attorney Joe Kashi received his bachelor’s and master’s degrees from MIT and his law degree from Georgetown University. Many of his technology and photography articles can be accessed through his website, http://www.kashilaw.com.

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