For color reproduction with this type of subject, use an ultraviolet absorber over the light source in addition to a UV filter over the camera lens. 2B over the flashtube of a small electronic flash unit. For larger light sources, try using a material with a UV inhibitor, such as Rosco Product No. 3114. It is caused by high reflectance at the far-red and near infrared end of the spectrum, where the eye has little or no sensitivity. Examples of problem subjects from nature are blue morning glories, gentians, and ageratum flowers, which often reproduce poorly because most color films are much more sensitive than the human eye to the far red.
Some organic dyes have high reflectance in the far red.
These dyes are often popular with fabric manufacturers because they are relatively inexpensive and work well with synthetic materials. While the high reflectance in the far red and infrared is found in all colors of these dyes, the effect is most prevalent in shades of green and blue. The far-red reflectance neutralizes the green or blue appearance, so the fabrics may reproduce as neutrals or warm colors. It is possible to check for high reflectance at the far-red end of the spectrum by making tests under actual working conditions. Make test shots with the film you plan to use for the final photographs.