Color Management Workflow in ErgoSoft RIPs

Color Management Workflow in ErgoSoft RIPs

Introduction

One of the most important factors of large format printing is ouput color fidelity. Print output not only needs to show vibrant colors but these colors need to be the same across a wide range of different materials and printers.
To achieve this, the ErgoSoft RIP offers an expertly designed color management workflow and industry leading tools for output calibration, ink amount control and color fidelity.

The Color Engine

Most printers supported in the ErgoSoft RIP use a CMYK based color model, usually CMYK including light inks and/or additional full tone inks. The ErgoSoft RIP therefore needs to send print data in the same color combination that the printer uses for it to be properly understood and printed. In addition to the original color recipe as a mixture of the available colors, the RIP needs to take into account that the inks and media type that is used by the printer will alter color appearance, and therefore adjust the mixture accordingly to ensure color fidelity. This is the main task of the color engine.
To achieve this, the ErgoSoft RIP color engine internally uses the device independent Lab color space. Ideally, Images from any color space other than CMYK (CMYK, RGB, LAB) are converted to Lab values using input profiles that define the color space the image comes from. The ErgoSoft RIP then takes the resulting Lab values and converts them to printer output data in CMYK (or in rare cases RGB) values made up of the printers colors using a printer profile for the printer/ink/media combination that is used.
This process of adapting image color values from their initial color space into Lab and then to the printer color space ensures that a printed image will look approximately the same on all media/ink/printer combinations.

Different Types of Color Conversions

Different types of conversions pose different challenges to the color engine to transfer colors between color spaces. Some conversion are simpler while others are more complex.

RGB Input - CMYK Output

Due to the radically different color model, RGB colors must be fully converted in order to print them on a CMYK printer. While it is always preferrable to embed the proper RGB Input profile into the file itself and use that, the ErgoSoft RIP also comes with a standard RGB profile that is active by default and used if no other input profile is defined.
In this type of conversion, the RGB color values in the image file are first converted to LAB, based on either the embedded input profile or the standard RGB input profile set in the ErgoSoft RIP color management settings. From LAB, the ErgoSoft RIP will then use the printer profile to convert these LAB values to the printers color channels and apply the density linearization to ensure that a suitable ink application.
Note that if no printer profile is selected, a standard LAB to CMYK conversion is used. This usually results in passable CMYK results, but does not use any additional colors the printer may have.

CMYK Input with Input Profile - CMYK Output

Technically, CMYK colors would not need to be converted to be printed with a CMYK printer as colors are already in the correct format. However in real applications, the CMYK color space of an image file will usually differ from the one of the printer, due to the influence that printer technology, inks, and media have on the actual printed colors. It is therefore recommended to use an input profile to define the image color space even if the image is in CMYK.
In this type of conversion, the CMYK color values in the image file are first converted to LAB, based on either the embedded input profile or the standard CMYK input profile set in the ErgoSoft RIP color management settings. From LAB, the ErgoSoft RIP will then use the printer profile to convert these LAB values to the printers color channels and apply the density linearization to ensure that a suitable ink application.
Note that if no printer profile is selected, a standard LAB to CMYK conversion is used. This usually results in passable CMYK results, but does not use any additional colors the printer may have.

CMYK Input without Input Profile - CMYK Output

Technically, CMYK colors would not need to be converted to be printed with a CMYK printer as colors are already in the correct format. While it is often best to use input profiles even on CMYK images for better color fidelity, there are some applications where not using one can be beneficial.
In CMYK, if no input color profile is used (Input Color Profile is set to "None" in color management settings and "Use embedded" is turned off), the program will not transition the CMYK values of the file LAB first as in other types of conversion. Instead, the CMYK values will be directly transferred to the printers color channels, even ignoring the printer output profile and only applying the density linearization to ensure suitable ink application.
In short this means that if input color profiles are turned off for CMYK, no color management input nor output is applied to CMYK images and only the density linearization is used. 

Any color space - RGB Output

The ErgoSoft color engine only offers limited support for RGB output. As such RGB output relies on external tools and sources for RGB profiles such as those offered in Windows printer drivers or proprietary Contone drivers offered by some manufacturers such as HP, Canon, Epson, Durst and Caddon.
For these types of applications, the ErgoSoft RIP will transfer the input color space to the default LAB space and then pass on the LAB values to the external engine (e.g. RGB driver) to process and transfer the values to the output RGB. The transition to output values in these cases does not involve the ErgoSoft RIP color engine and the ErgoSoft RIP has very limited influence on the actual output as neither density linearization nor ErgoSoft color management can be applied. Other features such as color replacement are also only available in a very limited fashion.

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