If you have normal vision, you’ll be able to see a wide range of different colors, all the way from a deep violet at the lower end of the spectrum, to a primary red at the higher end. In between these two extremes, you can see blues, greens, yellows and shades of orange. Put them all together and you have the visible spectrum, sometimes known as the ‘color gamut’ of your vision.
It’s quite a wide range, and most man-made devices have a smaller color gamut than the human eye. The most important gamuts for photography enthusiasts looking to reproduce their work are those of monitors and printers. These devices use two completely different ways of creating colors, known as additive and subtractive, and failing to understand these can impact your final print quality significantly.
Additive Color
This system is employed by devices which use light, like cameras, monitors, scanners and projectors – the color gets closer and closer to white as more shades are added to the mix. Light-based devices use three primary colors: Red, Green and Blue (RGB) and mix them at different levels to make all the other colors. With full levels of R, G and B, the mixed light appears white.
Subtractive Color
This is the way which printers work; as you will see it is completely different. These rely on reflected light and anybody who has ever painted knows that as more colors are added to the mix, it gets darker, not lighter. Printers use three ink colors: Cyan, Magenta and Yellow (CMY), but because they aren’t completely pure, they give a dark brown when mixed. This is why most printers add a true black ink to improve the quality of dark colors and to print black text. The initial ‘K’, from ‘blacK’, is used in the abbreviation CMYK, to avoid confusion with the ‘B’ in ‘RGB’.
Photo printers often add extra colors in other parts of the spectrum, such as light cyan and light magenta, to improve rendition of paler shades in skies and skin tones. So if you’re aiming for higher quality photo printing, looking for dedicated machines with more than the standard CMYK is a great place to start.
Turning Your Photograph Into a Print
To reproduce the image from your monitor into a photograph on paper involves matching colors between these RGB and CMYK systems – which in itself is a difficult task! If you’ve ever tried to use specialist color matching software you will be well aware of the problems that can occur, and if you don’t know what causes these limitations it can be a very frustrating task. So it’s time to delve into color spaces, and how they impact your prints.
Color Spaces
The gamut of colors a device can produce can be represented as an area in a shark’s fin diagram, like the one on this page. The full, colored area inside the diagram represents the range of colors the human eye can perceive. On top of this, and well within its borders, are three triangular (ish) shapes, which show the gamuts of certain color spaces defined for different devices or color standards.
The shape bordered by the blue line is the standard Red Green Blue (sRGB) colorspace, which was defined by Microsoft and HP in 1996 and was tuned to the gamut of colors that could be displayed by typical cathode ray tube monitors of the time. It is still used widely for general home and office monitors.
The Adobe RGB triangle, which has an orange border in the diagram, defines a larger color space, more suited to the graphics professional, at which the company aims most of its graphics software. The larger area of this color space, which was defined in 1998, includes many more colors, so a device which supports the Adobe standard will have a higher specification than an sRGB-only device.
Finally, there’s the color space supported by a typical ink-jet printer, which is similar to the Adobe RGB color space and shows the gamut of colors that you should be able to reproduce on paper. If a shade you try to reproduce on paper lies outside the color space of your printer, the color matching software will pick the nearest shade it can, for the best approximation.
Even with a quick glance it is easy to see the colors from Adobe RBG that a four-color inkjet printer is unable to reach. Couple this with the restricted gamut of a standard RGB monitor, and you get a general idea of the limitations you are working under. However, if you understand the differences between these color spaces, and why images will look different from your camera screen, to monitor to printed version, is a great way to begin the steps to better prints.
