DCF Full Spectrum; Does It Bridge The Gap Between RGB And The Eye?

According to the folks at Tribeca Imaging Laboratories (TIL), digital cameras (and I might add many types of film) "can't see purple." They go on to say, "The digital color model generates a limited spectrum. Any user can confirm this by simply pointing a camera at a deep blue or purple object and comparing the colors on the camera's LCD or computer screen to the
original subject."

While those of us who have tried to photograph chrysanthemums on film in the past know about this purple thing, the TIL crew decided to do something about it. They conducted years of research and came to the conclusion that the issue is not camera specific. Indeed, they concluded that the limited spectrum response was common to all digital cameras, dubbing digital color "universally inaccurate." Their response is the DCF Full Spectrum plug-in for Adobe's Photoshop, which works on both Mac and PC platforms. They claim that by using DCF Full Spectrum in Default mode that the photographer will get the most accurate possible colors from digital images, shot in sRGB or Adobe RGB.

DCF Full Spectrum Panel

The control panel in DCF Full Spectrum allows for manual control of color, plus has Spotlight and Fill sliders, which behave like the Shadow/Highlight control in Photoshop.
© 2005, Grace Schaub, All Rights Reserved

Although, according to TIL, RGB can produce millions of color combinations, the inaccuracies occur throughout the visible spectrum, and is particularly evident in violets, indigos, blues, and greens. Their software is a "color difference model" that is said to correct for the inherent shortcomings of the RGB model. It is "device independent" and works within the RGB "infrastructure" by remapping every possible color in RGB from its default to a corrected RGB triplet.

We worked with the DCF (Digital Color Fidelity) software and found that it did indeed alter the colors on screen, and that "live" demos (having the subject in front of you when you take the shot and use the software) show a decided shift toward truer color fidelity after application. Showing them on the printed page, however, would be problematic, as the subtlety of those shifts generally would not show up in the classic before and after setup.

There are three main choices in the DCF plug-in, which after installation is accessed from the File>Automate menu of Photoshop. The default is an application of DCF called "Full Spectrum," which runs a routine that opens up greens and alters blue sky. The odd thing is that you are not sure just what has occurred, as the image you begin with on screen has often become more familiar than the "original" scene as you saw it, so it can be hard to judge if the correction is gratuitous or meaningful. The main issue for this writer is not always absolute "true" color, a discussion of which can open a whole can of worms, but whether the color serves the content and desired mood of the image. For others, "true" color may be more meaningful or necessary.


The changes are quite subtle on most shots, and it can be difficult to see in print, but the richness of this rainbow scene before and after application of DCF Full Spectrum is apparent to this writer's eye. The question is, just how important is true color to you, and is RGB color as shot, even though perhaps not "true" color as seen by the eye, sufficient? Each photographer will know the answer to that for him or herself and whether their work requires the DCF treatment.
© 2005, George Schaub, All Rights Reserved


In any case, the program does seem to allow for the enhancement of certain types of images, mostly nature and scenics, and should be of interest to those who like to work outdoors. However, studio product, fashion, and the like photographers, where spot on color is necessary, will also benefit. The major differences are in the lower frequency colors mentioned earlier.