Color Management
 

Ever viewed an image on-screen, then printed it only to find that the colors on the print-out look completely different?

Human vision is made possible by the presence of light sensitive cells in the eye called rods and cones. The cones are responsible for color vision. There are three different types of cones in the retina – red, green, and  blue. All other colors we see are mixtures of these three. For instance, white is perceived when equal amounts of red, green, and blue are seen. The amount of color we see also depends on the strength, concentration, and position of the light source. Lighting conditions can have a profound effect on the perception of color.

The human eye is often able to detect many more colors than digital devices can reproduce. For instance, if you look at a blank, white page of paper, your eye is probably detecting at least 100 distinct shades of white. Most imaging devices can generate/detect millions of colors; however, the manner in which these colors are broken down into components and representated may differ. These representational models are are called color spaces.

Because different devices use different color spaces, they may display the same image differently. For example, if you have a digital image that you created on your display, it may be in a device-dependent RGB color space. If you want to print it on a printer, it must be converted to the printer’s color space, usually a device-dependent CMYK color space (cyan, magenta, yellow and black). Even though the printer may use the CMYK color space, the colors it renders for specific CMYK values are often slightly different than all other types of printers. This is where the concept of Image Color Matching comes in. ICM ensures that a converted color is matched to its visually closest color in the destination color space. This process is called color matching.

When printing, Chasys Draw IES lets Windows ICM do the color matching using information collected from the software for your printer. One key thing to note about ICM is that it attempts to convert colorimetric information from one color-space to another – the results are not necessarily perfect. Because of this, it is usually necessary to print a draft – and make any necessary corrections – before you print out your final masterpiece.

Traditionally, designers have overcome these challenges by doing all their work using color settings that match those of the printing press they intend to use. One would begin designing a piece of work by setting their image editor to represent colors in the working space of the printer. All editing would be done in this space and as a result, the final output would be similar to what the artist saw on the screen.

While this method is preferred by large production houses, it is not without its shortfalls:

• Most modern devices, including monitors and digital cameras, produce output in sRGB, forcing the artist to first convert all their files to the target space before editing begins.

• Different printers use different color profiles. Thus, such work is not portable.

• The color output of a printer is affected by many factors that are bound to change over time and even with each print. It is therefore very easy to end up with wrong colors even if this process is followed to the letter.

• Getting the color profile used by the printing press can at times be a challenge.

But the debate continues between content creators and print providers. While creative people are excited by the flexibility and cost benefits of an open color-managed workflow, they’re often faced with uncooperative or downright resistant print providers. Many print shops have no clue how to handle ICC profiles, are not prepared to receive RGB files, or firmly believe that a CMYK workflow is the only game in town.

sRGB is a standard RGB (red, green, blue) color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the world-wide web. It was subsequently standardized by the International Electrotechnical Commission (IEC) as IEC 61966-2-1:1999. sRGB is the current defined standard colorspace for the web, and it is usually the assumed colorspace for images that are neither tagged for a colorspace nor have an embedded color profile.

RGB working spaces provide a good environment for editing images. They have two important properties that aren’t shared by the vast majority of device spaces:

• Gray balance. RGB working spaces are gray-balanced, meaning simply that equal amounts of R, G, and B always produce a neutral gray. This is hardly ever the case with device (scanner, camera, display, printer) spaces. Since one of the easiest ways to bring color into line is to find something that should be neutral and make it so, gray balance is an extremely useful property.

• Perceptual uniformity. RGB spaces, and particularly sRGB, are approximately perceptually uniform, meaning that changing each channel’s numeric values in the image by the same increment results in about the same degree of visual change, no matter whether it’s in the highlights, the midtones, the shadows, the pastels, or the saturated colors. Again, device spaces generally don’t work that way.

Due to these advantages, the ubiquity of sRGB and the rise of social media and heavy use of photographs on the internet, the current trend in industry is towards an sRGB-centric workflow. In this model, source artwork stays in the sRGB working space for as long as possible. All color corrections are performed in this space, converting color only when targeting for various final outputs that may include websites, high-quality inkjet printing, and printing on press.

Adobe RGB is a color space developed by Adobe Systems, Inc. in 1998 in an attempt to bridge the gap between sRGB and CMYK color spaces. It encompasses the same number of colors as sRGB but those colors are more spaced out towards the green end of the spectum. In other words, it squeezes colors into a smaller range (effectively making them duller) before recording them to your file, with the reverse process being done when reading the file. This allows the display of richer greens and cyans, but at the cost of greater color quantization. Although this should theoretically give deeper colors, in practise, it usually does not, and even minor mistakes in the workflow will result in much duller colors.

Very few equpiment and software handles Adobe RGB correctly, so the results are most often disappointing. Furthermore, very few printers and print material can take advantage of the range extension, so in practice, you’ll rarely ever see a tangible benefit to using it. You will, however, see some articles that still advocate for its use, often based on the wider gamut argument.

Chasys Draw IES is a sRGB editor; it does all its internal operations in the sRGB color space. As hinted above, this choice is based on the fact that all modern equipment is designed to work with sRGB out of the box and you don’t really need to be messing around with color-spaces because doing so will generally result in poorer results than just sticking with sRGB from camera to print. Other color-spaces are only used when inputting from or outputting to external devices. Resultantly, the intent is that you do all your work in sRGB and only have it converted to a device-specific color-space at the moment of printing. The advantage of this is uniformity and portability of the resulting work. However, there are situations in which you may need to see what a work will look like on paper AS you design it, NOT AFTER you’ve done so. This is where Live Proofing comes in.

Printers generally can’t match the fully range of colors that a display monitor can produce. When a color-managed printer receives input in sRGB, it outputs what it can as is, and converts what it can’t to the nearest equivalent. This means that if the input sRGB only contains colors that are reproducible in the native color space of the printer, then the input sRGB is just as good as input in that native space. Live Proofing allows the editor to clip the sRGB image to the gamut of the output device, letting you see the image not as it is, but rather as it will appear once printed.