Printing with Contone

Printer manufacturers invest a significant amount of time and money into creating contone print modes in order to support sales of their ink and media. To make it really easy for users to get great quality output with little time and effort, the printer manufacturer has to configure complex default internal processes within the printer hardware. This means that the printer can assume which type of ink, media, and mode combination is best for the desired output.Again, this output is only designed for use with the manufacturer's brand of ink and media.

If you're using a 3^rdparty media, you're hoping that the characteristics of this media are similar to the built-in (i.e. manufacturer) media types. If the characteristics are not similar or not compatible, then you may not get acceptable results. In this case, we recommend using a halftone workflow to get the best results.

When profiling or configuring media and modes for use in a contone workflow, the software only displays options that are valid for the contone modes as selected in the Printer Settings dialog. In many cases there will only be one or two choices.A contone media profile includes the same elements as a halftone media profile except that some of the elements may actually be stored and used internally to the printer such as ink restrictions, linearization, and ink limiting. This allows the printer to internally maintain it's calibration if an on-board calibration device is present.

Note: You cannot nest halftone and contone jobs together for printing at the same time. However, they can be printed as separate sequential print runs without the need to change media selection in RIP-Queue.

Using the Clone Tool

The clone tool within Media Manager allows you to determine if any installed media can be reused to give you acceptable output quality by printing a test file while utilizing the original media profile properties. If your workflow consists of 3^rdparty media you might find the clone tool to be very useful. You can print with your existing media profiles and all of the different modes in your library on your 3^rd party media and review the output quality then choose an existing media that works best.

By giving a new unique name you can create a new media that essentially copies the output of an existing media. Please be aware that a cloned media doesn't represent a color-managed characterization of the media. We recommend performing a recalibration to ensure optimal results.

While cloning a media profile is one option to profile your media, creating a custom media profile is the best option when you want a unique ICC. The existing media profile may work well using the same ink restrictions, linearization, ink limits, and ICC profile, but a different media may require different settings. A clone utilizes every aspect of the profile and you may only need a new ICC for your specific output needs.

Profiling with Contone

The great thing about contone is that it makes it easy for you to profile, especially when you use the manufacturer ink and media combinations. A 3^rd party photo gloss may not act like a manufacture photo gloss because of the different coatings and media thickness. Remember that each media has its own set of characteristics and may require different ink restrictions, linearization, and ink limits.

The printer manufacture has already spent many hours in R&D time to fine tune the default settings for their contone print path. They theoretically have their own .PrnInst inside the device for their own media. The RIP simply sends the contone data to the device and the printer knows what to do to produce beautiful output.

Generally, you can profile a contone media with almost the same steps as you would a halftone media. You can omit the need to evaluate ink restrictions and continue with the workflow by clicking > Next through the wizard. You must still perform the linearization step to create a table that allows external recalibration. Generation of an ICC profile is required with contone print paths if ICC color management is to be used with the print mode.

You can potentially have both contone and halftone modes in the same media depending on the printer and the type of output. Contone and halftone modes can only co-exist in the same media if the ink configurations related to the modes both specify the same number and type of process channels (i.e. they must be compatible with the media's ink configuration), and the number of process channels in an ink configuration is usually independent of the use of light inks. RGB, CMYK, and CMYKRGB (for example) are incompatible ink configurations and therefore print modes that use each of these ink configurations will need to belong to separate media groups.

Getting Started: Printer Capabilities

If you choose to create your own media profiles using contone, review the options within Media Manager > Printer Capabilities and enable the contone dot pattern, resolution, and ink configuration you wish to use. This will also give you an idea of your options before you begin which allows you define your profiling purpose.

Within the Printer Capabilities > Resolutions window, enable the desired resolution with "CT" as this denotes a contone resolution. We have added these additional resolutions and you must enable them if you plan to profile using a contone print path. The reason for having separate contone resolutions is because the dot patterns you enabled in setting up a print mode are based upon the resolution.

The ink configuration also needs to be compatible with the resolution. An Ink Configuration itself is defined on a media level not on a mode level. It is usually defined as "the ink set currently loaded in the printer" and can be organized within media groups.

Most media profiles use CMYK process data including printers with light inks regardless if they are CMYK contone or halftone. If you are creating a media using RGB Contone, you must enable and use the CMY process option.

Choosing RGB or CMYK Contone print path depends on how your specific printer handles the data. RGB may process faster because it is only using 3 channels over CMYK which processes 4 channels. The main difference is the use of black generation with CMYK. You may see differences in the actual output, so if your printer allows for both print paths you may choose to test each one separately to see which one you prefer. 

RGB Contone profiling

PROS: This workflow is quick and utilizes the RGB inks. (i.e., ICC Only).
CONS: There are few ICC Build Options related to Black available to RGB Contone. This can lead to poor shadow detail and hard transitions to full black. May appear hazy, or slightly posterized.
*Initial Media setup uses the "RGB Contone" Ink Configuration, with a Process Colors setting of "CMY". The dot pattern is "Contone".

CMYK Contone profiling

PROS: This workflow is similar to RGB Contone, but only uses CMYK inks (i.e., No Ink Restriction, Or Linearization). Additionally, there are more ICC build options available for controlling shadow content.
CONS: It does require an Ink Limit because it uses much more ink. You need to enable the dot pattern within printer capabilities before you begin or when you get to modes options the fields will be blank.
HINT: Adding a Linearization may give slightly better output in some cases.
*Initial Media setup uses the "CMYK Contone" Ink Configuration, with a Process Colors setting of "CMYK". The dot pattern is "Contone".

IMPORTANT: Because the Ink Restrictions are reliant on the built in media, Contone may be a poor choice for 3rd party media!

Create a New Media and Set Mode Options

Use the wizard within Media Manager once you have enabled your options. From the Media Manager home page click > Create Profiles > Create a New Media. Choose the Media Group from the drop down list and give the media a unique name. Click > Next to continue.

During the profiling workflow, you must choose a contone resolution to enable the drop-down list of contone dot patterns. You can do this while defining your mode options.

The profiling workflow steps are very similar with contone and halftone except for the Ink Restriction step. A halftone print path gives you control over the ink load and allows you to maximize gamut while this is not necessary the case with a contone print mode.

Calibration

With contone, the printer assumes the ink restrictions based on the media type and mode options and the wizard skips to the calibration/linearization step which requires you to print and read a test swatch.

Although the printer has already defined the proper ink distribution, you may calibrate the printer and build a linearization table in order to recalibrate this media in the future. Once you have built the linearization table, click > Next to continue.

Note: When using Contone with RGB ink configurations you are essentially printing through a profile in the printer and do not have direct access to output channels. Linearization will attempt to linearize the RGB/CMY data paths that don't correspond to single ink channels. Therefore, it usually doesn't make sense to linearize RGB contone workflows.

Ink Limits

This next step usually allows you to control 3-4 color combination by analyzing the ink limit swatch. Again, the printer has already pre-determined the proper ink restrictions which also translated into the optimal ink limits and overall ink load for the media.

Click > Print Swatch to produce the test swatch, then click > Read Swatch. If you notice any bleed in your output you will need to change the default settings. As mentioned earlier, there is rarely a need for ink limiting; in our experience we have usually left the Basic Ink Limits at 4. Review your swatch and make your determination, click > OK to close the Read Swatch dialog and click > Next to continue.

ICC Profile

When you print your ICC swatches, remember to choose color sampling device you plan to take your measurements, especially if you have multiple devices configured. We also recommend you click the Setup button and review the options tab before you click print. On the options tab choose the "Ultra Accuracy with linearization" (2463 patches) and enable the Scrambled Swatches option.

Print and read your swatches as normal. Before you build the profile, click the Options button to review the default ICC build options. See -"ICC Build Options" for more information: http://onyxgfx.com/kb.pl?cmd=view&kbid=202.

Profiling Contone Conclusion

The contone mode is easier to profile, but you have a lot less control over how ink is used. The RIP no longer controls the light and dark ink levels, the ink restriction values, and in some cases the use of black ink and hi-fi colors. The RIP can aid in ink limiting to some extent if there happens to be any noticeable bleed, but this is rare.

When you use a 3^rdparty media, you are using the same assumptions for similar media types and outside of those predetermined characteristics; it may or may not work well for you. You may also be limited in the mode options you wish to use as defined by the media type.

In these cases you have the option to use the halftone mode. With the halftone mode you have the control to adjust for whatever problem you might encounter in the third party media. When you use the halftone print path all options are open to you including available resolutions and other mode options. The accuracy with the halftone dot and maximizing the printer's output gamut may be preferable.

Advantages and Disadvantages
One of the other things you have with the contone dot patterns is that you have the ability to RIP at a lower resolution and print at a higher resolution. Which is really essentially the contone dot pattern creating virtual pixel duplication; this is a really nice advantage. If you're doing large output, you can RIP at 3000 dpi and then send it down and print at 1200 dpi. There may be some aliasing but in essence the dots are really small and you retain the fidelity and significant time savings with the speed.

Going through the contone mode is much easier because you're using the printer dot pattern. The printer may have both error diffusion and a stochastic and which one gets used is determined by the printer and is mode dependent. The printer makes this choice, not the customer.

You have a lot more flexibility with the halftone that you do not have with the contone modes. With ONYX software, we give you the tools to create a media profile that maximizes the gamut of the printer when using a halftone print path. It may not be always the most desirable results and it may be harder to do because you need to make individual choices on each media when setting ink restrictions, setting ink limits, and settings used to build an ICC profile.

Not only the dot pattern, but the print direction is also mode specific and uni-directions or bi-directional can only be chosen depending on the mode used. For specific media types you'll only have certain resolutions and for those resolutions you'll have specific settings available for print direction. These choices are all enforced by the software. You can only use valid options as determined by the printer manufacture.

Trade off using Contone sometimes is referred to the difference between speeds vs. control. Most contone print modes do provide both and give excellent quality results. In some test prints you may even see that a contone print is "smoother" than a halftone print in some areas.

Basically when you use a contone mode you don't know if you're getting the maximum gamut for that media. (In 7.1 we don't have a way to set ink restriction within contone; we may add that in 7.1.2, because we can add the ink restriction within the printer driver). With CMYK Contone profiles we create a linearization table so you can recalibrate, but for the most part we haven't needed to do much.

One advantage is that we have greater throughput because we're off loading the processing to the printer. With contone you loose the control and the ability to use ink counting.

Note: One of the down sides of using Contone is that we're sending 8-bit data to the printer. If we've linearized the data then we have less than 256 levels because linearization is going to reduce it down there. What can happen is with the contone modes you can end up with a little more banding in your gradients.

With the Stochastic dot pattern and the halftone print path, since the linearization is actually applied as part of the halftone dot pattern we actually have all 256 levels. Available to use so it's a little less banded.

Using Contone and a tiff image you gain the ability to start printing almost immediately. With PS image you still need to RIP the contone data before sending it to the printer, but the RIP doesn't need to halftone the data so the image begins to output sooner and it's faster. If you're using RIP and Print on the fly it will usually be able to keep up.

Comparing Contone Mode and Halftone Mode Output
When comparing output between Contone and Halftone output modes it is important to remember that differences are made up of differences between ink load, ink separation, drop size usage, in addition to dot placement. Among other things color gamut, smoothness, and print image artifacts (like bleeding, banding, etc.) are affected.

For example:

• Larger gamuts can lead to bleeding
• Smoother output can lead to banding
  

Trade-offs are made between competing interests which can lead an image printed using different modes to appear better/worse in different areas of the printed output. In many cases there is no one right way of doing things. Some areas appear better with one mode and other areas appear better with another mode.

The printable gamut is largely determined by how ink load is determined and how color separation (use of black inks/hi-fi inks) is performed. If the level of control is similar the color results should be similar. Differences in control and how the control is used can be used to explain many of the differences.

Differences in smoothness are attributable to many things. Differences in ink separation (use of black ink/hi-fi inks), ink restrictions, variable dot usage, and the dot pattern placement all have a part in determining smoothness. In some instances if you can get similar colors when comparing different output, then you can go a step further and analyze the dots for smoothness.

Printer Specific Observations
The reason why printer manufacturers have developed their own contone modes is they want to make it as easy as possible to use their media.

Canon - There are two different contone media groups: CMYK Contone and RGB Contone.

CMYK Contone - CMYK Contone on the Canon you don't have access to the Red, Green and Blue inks, it is only going to print using Cyan, Magenta, Yellow and black inks (plus light inks). When we're printing with contone we're essentially printing through a profile. If it's CMYK, we're sending CMYK data through the printer profile,

RGB Contone - With RGB Contone there is access to all the inks in the printer, but we've lost direct control of the ink separation including control of the black ink, but one benefit is that we're sending ¼ less data to the printer. The RGB data sent to the printer is essentially sent through an internal printer "profile" table to provide the ink separation and final output. Because of this it's not entirely clear what the "RGB" means. We therefore still need to profile RGB print modes in order to get an external characterization of what each RGB combination will print. From this we will have an understanding of what to send to the printer for any desired L*a*b*, and color management in the RIP is possible.

Because we don't have control over the ink and we would hope that we're maximizing the printer's gamut, but this is dependent on the printer. With RGB data we have no control over the black generation and some of the other ICC Build Options are disabled. Black generation can have a lot to do with determining you overall gamut. This is one of the main reasons why we have a unique black generation for controlling Achromatic and Chromatic colors in the profile which are not available with RGB Contone.

With Seven colors, your color separation can also play a part in making the contone driver seem smoother. Dot appearance is more than just halftoning; especially when you're using seven plus colors. ONYX is still working on the greater than four color separation profiling technology.

EPSON - Processing support for the EPSON Stylus Pro 11880 includes ONYX halftone dot patterns (I.E. stochastic, FDRP, Screen, etc), the contone dot pattern, and the EPSON OEM dot pattern. The EPSON OEM dot pattern uses the same dot placement technology as the Contone dot pattern, except processing is performed on the RIP's computer rather than inside the printer. To enable the OEM dot pattern for use with halftone select Media Manager > Printer Capabilities > Dot Pattern > Enable OEM Dot Pattern.

The Contone dot pattern modes acts like virtual pixel resolutions, such that the resolution of the data that is being sent to the printer is usually smaller than the resolution of the dots being output by the printer. In many cases you do not have access to sending the contone data at the higher resolution.

With the OEM dot pattern modes you always process at the final output resolution that you are printing at. It might be possible to get better quality using the OEM dot pattern over the contone pattern since you have access to processing at higher resolutions.

EPSON has traditionally provided to developers the ability to do the halftone processing at print time (essentially acting like a contone print driver where expensive halftone processing takes up the RIP's CPU cycles). This mode of operation is not used by the ONYX RIP because multiple copies end up being multiply processed.

Instead, a special implementation of the EPSON OEM dot pattern was jointly developed by EPSON and ONYX Graphics to allow halftone processing to be performed separately from printing (similar to how processing is performed using the ONYX dot patterns). This allows the halftone processing of a single copy of an image and only the halftone data being duplicated for additional copies. Note: During the ONYX RIP printing feature still only halftones a single copy and multiple copies duplicate the halftone data.

Processing support for the EPSON Stylus Pro 4880, 7880 and 9880 includes halftone dot patterns and the EPSON OEM dot pattern. They do NOT support the contone dot pattern with halftone processing performed in the printer. The EPSON OEM dot pattern technology for the 7880 and 9880 is the same as on the 11880.

With both the contone and the EPSON OEM dot patterns it's paramount to remember that the available dot pattern options are limited to what EPSON has profiled for the printer for each printer device and media type. Options include resolution, dot placement (error diffusion/dither), and print direction (bi-directional/uni-directional). You can not unlock other capabilities than those hard coded for each media type.

For example, on glossy Medias you can only have high resolutions and on plain paper you can only use lower resolutions. If you want to have better productivity in terms of print speed, the contone may not give you access to the lower resolutions or bi-directional printing, or number of passes. If you choose to use an ONYX halftone dot pattern you can select any of the available resolutions and print options to profile for a specific purpose.

HP - For the HP Z-Series printers, the available options for halftone dot patterns (IE resolutions and print settings) are generally restricted to options that are available in the contone dot patterns (much to the chagrin of those who might expect otherwise). This becomes a limiting factor for those who wish to develop their own workflow settings outside of what HP has provided. In many cases there is not much more control for halftone workflows than there is for contone workflows. At some future time it is hoped that HP will provide more flexibility for halftone workflows outside that provided for the contone workflow since a third party is providing all the settings needed to profile and get acceptable output.

The contone resolutions provide the option of virtual pixel resolutions with separate process and print resolutions. Lower process resolutions provide for much improved throughput with the sacrifice of high detail in images through pixelization.

The contone dot pattern for the HP Z3100 provides access to CMYK and RGB data being sent to the printer. These ink configurations make use of all the inks in the printer. With CMYK data transfer access to black separation is possible. With RGB data transfer black separation is lost, but a there is a reduction of ¼ the amount of data needed to be transmitted to the printer.

*Recap -*In summary, here are some examples of why you might choose either the Contone or the Halftone print path:

Benefits of using Contone

• Manufacturer media defaults use predetermined mode options means you get good results with media types defined by the printer.
• The mode options only display valid settings for media profiles within the RIP.
• Printer does the halftone processing on the device
• Uses manufacturer dot patterns and resolutions tested to produce good quality.
• Allows printer hardware to upscale resolution for speed on large output.
• The ink is controlled by the printer settings per media type which means when you create custom media, the printer has defined which modes and options are valid to produce optimal results.
• No need to determine Ink Restrictions and rarely any need for ink limiting because most models use internal calibrations which means you can go straight to ICC step when profiling.

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