By Ron Ellis
DeviceLink profiles are nothing new, and have been with us for years. (A DeviceLink is a type of International Color Consortium profile that contains two profiles inside of one). Although DeviceLink profiles are powerful, many users are not familiar with them. Perhaps color management software is just catching up to where it can take full advantage of the powerful uses for these profiles, or maybe the timing is now just right. Either way there are a number of new color management applications that use DeviceLink profiles, and because of this it is worth taking a new look at DeviceLink profiles.
A DeviceLink profile is a type of profile that contains two profiles, and the ability to create these profiles is usually a special option inside of most color management software. In order to create a DeviceLink profile, you select the two profiles, along with settings, and then save these ÔlinkedÕ profiles as a DeviceLink profile. A DeviceLink profile always contains a source color space and a destination color space, and the conversions always move from the source color space to the destination color space.
Currently DeviceLink profiles canÕt be embedded or assigned in applications like Photoshop because they contain mathematical information for a color conversion rather than describing a color space. Because of this, DeviceLink profiles are more complicated and less flexible than traditional ICC profiles and are classified by the ICC as a special type of profile.
In order to create these, you need software such as LeftDakotaÕs Linkolater, ColorThink Pro, or special options for Monaco Profiler or ProfileMaker. Not only is special software required to create these profiles, but only some software and RIPs can take advantage of DeviceLink profiles. If these special profiles are so much more difficult to use, then why would anyone ever use DeviceLink profiles?
There are some very unique things that DeviceLink profiles can do that you cannot do with other types of profiles. The first has to do with color conversion. DeviceLink profiles tend to produce more accurate color conversions than two separate profiles when used within a proofing RIP. For example, if I choose a paper profile and an input profile in a typical RIP, I will hopefully get a reasonably accurate match (depending on the RIP and the methods used to create the profiles). By creating a DeviceLink profile the color match is almost always noticeable better. Not all RIPs support this, but many of the high-end proofing RIPs do support this, and these ÔbetterÕ matches are often used by consultants to achieve better results.
The second main reason to use DeviceLink profiles has to do with maintaining channels in color conversions. Typical ICC color conversions require all of the colors in the file being converted — including the black channel. DeviceLink color conversions allow the user to maintain the K channel so that the color conversion can happen without any changes to the K channel — such as converting K type to CMYK type. This can be important when making color conversions for certain types of inkjet proofing where you need to maintain the black channel. It is even more important for making color conversions during plate generation. When used during ripping or plate generation, the black channel must be maintained and DeviceLinks are a must. In this scenario the DeviceLink is used to make the press simulate another printing condition, or to match a printing condition such as GRACoL. Not every platesetter RIP can use DeviceLink profiles, but many can, and for those with RIPs that canÕt, there are third party applications that can provide these conversions.
Examples of uses of DeviceLink profiles are found in many high-end prepress products today. The use of a DeviceLink profile in many RIPs actually provides a better color conversion, resulting in a lower deltaE when compared to the data you are trying to match or meet in a conversion.
Another use of DeviceLink profiles is to enhance color conversions on press. While plate curves (or gain curves) can be used to control color conditions on press, DeviceLink profiles can also be used to make plate conversions on press. While plate curves are simple and work well, there are certain color areas such as the three-quarter areas that curves cannot address, but profiles can. Many prepress RIPs allow the use of DeviceLinks to perform color conversions when generating the plate data.
A good example of this would be to use profiles to match GRACoL 7 rather than using plate curves.
Another use of DeviceLink profiles it to control or change the black generation in the source file. There are several major benefits to using Gray Component Replacement (GCR) and changing the separation prior to plating. DeviceLinks in this scenario can be used for several purposes. The first reason is to reduce press variation on press. When profiles with GCR are used, the files are re-separated.
During the reprocessing of the files, the black generation is increased and data is reduced in the color channels with this data being moved to the black channel. When this is done, the resulting files are less subject to variations caused by slight density variations on press. This technique is often used to reduce color variation on web presses as well as on sheetfed presses. A second benefit of this GCR is also related to the effects of black generation.
By turning GCR settings up users can also use this beneficial DeviceLink technology to save ink. While this may be less useful to sheetfed printers, it can provide substantial cost savings to web printers of all types. A conservative estimate is that you can expect 15 percent to 20 percent ink savings when using DeviceLink profiles.
In addition to ink savings, users also report less color variation as well. When using GCR with DeviceLinks, the more you turn up the level of black generation, the less color you will use. Obviously, there is a limit to how much color you can take out of a job without affecting color quality, but there is some latitude between the balance between the way most printers currently print and taking out too much color.
Most printers using this technology find that using GCR actually improves their quality and makes their printed product more consistent.
A number of products work with DeviceLinks. These include products by Alwan, CGS, GMG, EFI and others. For proofing the products are relatively inexpensive but for the more advanced press functions they can range from $10,000 and up. While many of these products are currently stand-alone products that sit in front of the RIP, there is no doubt in the future that these products will be built into every major RIP, and become a part of daily life in many printing operations.
About the author: Ron Ellis is a prepress consultant specializing in workflow training and integration. He can be contacted at 603-498-4553 or through his web site at www.ronellisconsulting.com.