Printing & color separating: technical details

Color separating

Xara converts RGB, HSV and grayscale colors to CMYK for printing. Because the inks in printers are not pure color, some color correction is required. For example, theoretically 100% red in RGB is 100% magenta and 100% yellow in CMYK. In practice, less magenta is required to get the right color. Also, in dark colors and grays, black ink can replace a proportion of CMY. Color correction in Xara is entirely automatic.

CMYK colors do not need color correction and so are usually printed without modification. The exception is areas where transparency has been applied. This is described in detail below.

Transparency and color separations

Transparency helps create some outstanding illustrations, but can also cause unexpected results when color separating, because PostScript imagesetters and printers do not directly support transparency. Areas covered by objects with transparency applied are output as an RGB bitmap. This bitmap is then color corrected and separated to CMYK. This process happens even to objects with 100% transparency.

This means that in objects under a transparent object:

CMYK color values change. This is particularly noticeable with black and grays which will then appear on all four separations rather than just the black separation.

Spot colors (and PANTONE COLOR BRIDGE colors) are separated to CMYK (and color corrected) (see PANTONE Colors for more on PANTONE COLOR BRIDGE).

Watch out for:

Objects under totally transparent objects. Instead of using 100% transparency you can use No Color (see The color line for how to apply No Color).

Text under a transparent object. Where possible, have text as the front object so these problems don't occur.

Intermediate colors in blends and fills

This section applies to all blends and multicolor fills. That is, all fill types except flat.

Normally, a graduated color fill mixes colors using the RGB color model. The exception is when both end colors are defined as CMYK. In this case, colors are mixed in CMYK. One advantage of this for grayscale blends. An RGB gray is printed as a mixture of the four CMYK inks. Defining the gray as a tint of CMYK black gives better printed results.

Rainbow and Alt Rainbow mix colors using HSV.

Three-color, four-color, fractal and bitmap fills always output as RGB bitmaps and are color-corrected. This means that any spot colors used in these fill types output to the CMYK separations, not to the spot separation.

Special rules apply for spot colors:

In blends: If either end color is a spot color, you can do fade mixes but not rainbow mixes (the reason is because you cannot alter the hue of a spot color).
In fills: If either fill color is a spot color, you can do fade mixes but not rainbow mixes.
In blends: If both end colors are the same spot color (or tints of the spot color), the blend outputs only to the spot separation.

In fills: If both fill colors are the same spot color (or tints of the spot color), the fill outputs only to the spot separation. Note: this does not apply to three-color, four-color, fractal and bitmap fills which output only to the CMYK separations.

If you blend or fill from a spot color to a non-spot color, Xara creates the requested blend. For example, if you blend from cyan (CMYK color) to gold (spot color) the cyan separation shows a blend from 100% color to no color and the Gold separation shows no color to 100% color. This is approximately what you see on screen (allowing for differences between screen and printer colors).

If you convert the blend to editable shapes, the intermediate shapes lose all spot color information. They separate only to CMYK. Only the final object prints as a spot color.

RGB and CMYK Blacks

Because shades of black and gray that are defined as RGB or HSV colors will separate into a mix of all four CMYK process colors when printed, you can sometimes get less than perfect gray shades. And any slight mis-registration of the CMYK color printing process will sometimes be visible on the edges of black objects.

Although the theory is that an equal mix of CMY inks will give a perfect shade of gray, it does not (and this is why the black "K" ink is added to the mix). So a gray that is defined as an RGB or HSV gray will contain a mix of all four colors to improve the gray color. But the best gray can be achieved by using only the K (black) ink plate. Thus if you require perfect grays it's better to use gray shades that are defined as a tint of a CMYK "pure" black.

When creating documents based on the default templates designed to be printed, such as US Letter or A4, then the shades of gray defined on the Color Line are defined to be tints of pure "K" black. So if you use these gray colors from the Color Line, you will get quality printed grays.

There is a corollary situation that a printed black that is based solely on the use of "K" ink, is not that black. You can get far darker blacks by adding some of the other inks printed on top of the black. So if you require really dark blacks for large objects or areas, then you can define a CMYK color that has 100% K ink and a percentage of the other colors (30% of each of the CMY colors is sometimes used).