Grayscale ICC profiles and soft proofing
Black and white prints have always been a weak spot for this technology. While top quality, fade resistant color inkjet prints could be made in the 1990s—by IRIS printers—or in 2000—when Epson introduced the first affordable pigment printers—getting neutral B&W prints was possible much later, with the first printers that incorporated multiple shades of gray inks and adequate driver support for monochrome output. Before that, only specialized methods were available, and they were both expensive and difficult to master.
Nowadays, it's possible to produce excellent black and white prints on any professional inkjet printer, with quality that easily matches the best chemical darkroom prints on fiber paper. Best of all, 95% of this quality can be obtained by sticking to the printer defaults and a professional paper from the same manufacturer.
Even so, there's still room for improvement. One of the techniques I've explored recently is the use of grayscale ICC profiles for B&W printing.
What are ICC profiles and why do they exist?
ICC profiles, or color profiles, exist to characterize how a particular device reproduces color and, ultimately, to allow software to compensate for that in order to output color accurately.
B&W ICC profiles do exactly that, but use a single table to describe the printer grayscale values, from paper white to solid black. These monochrome profiles allow us to linearize the printer output, compensating for minimal ink batch variations and printer manufacturing inconsistencies.
There are mainly two advantages of working with B&W profiles: output linearization and soft proofing.
Linearization ensures that your printer reproduces tone values evenly throughout the scale, from paper white to solid black. For example, if the 50% percent gray of a particular printer comes out as a 47% gray, we should output it roughly 3% darker to get a perfect tone. By describing a printer, ink, and paper combination through an ICC profile and printing with it, we are able to effectively make output linear.
Soft proofing is the holy grail of digital printing: being able to see in your display the exact simulation of your final printed output. Even though professional Epson, Canon, and HP printers come with dedicated black and white modes, none provide means for accurate soft proofing. This is where building your own monochrome profiles comes in handy.
How to create grayscale ICC profiles
Software and hardware needed:
Color profiled display. It's not possible to accurately preview your printed output without a properly profiled display.
Professional inkjet printer that has a dedicated black and white mode. For example: Epson R2880, R3000, Stylus Pro 3880, and other professional models; Canon PIXMA Pro9500 Mark II and imagePrograf series; HP Z3200 models, etc.
A suitable colorimeter or spectrophotometer, such as: Datacolor Spyder3Print, X-Rite ColorMunki, X-Rite i1, etc. This device will be used to evaluate the output of your printer by measuring a calibration target.
QuadToneRIP (QTR) to build the profile. This is an inexpensive ($50—shareware) software package dedicated to black and white output on inkjet printers. It includes a simple utility for creating B&W profiles that works even if your printer is not supported by QTR itself. In this guide, we'll be using this utility to create our ICC profile, but we won't use other QTR functionalities and will stick with the original printer driver for output.
Step by step instructions
Download the 21 step grayscale L* gamma target.
This target uses the QTR – Gray Lab color space, bundled with QuadToneRIP, which has a linear gamma response. This is my current workspace of choice for grayscale files. The linear gamma preserves shadow detail much better than a 2.2 gamma color space, like Gray Gamma 2.2, which I used previously. It is also impossible to obtain a perfectly linear curve when using a non-linear gamma, since, by function, gamma transformations compress tonal information in some parts of the scale. Read more about gamma correction here. (Thanks Mike King, on the QTR mailing list, for the tip.)
Print the target without color management and make sure to keep the original profile assigned when opening it.
If you’re using Adobe Photoshop CS5, this version doesn’t have the “No Color Management“ option on the print window. The workaround is to do a null profile transformation by outputting with the same profile as the image. In this case, in the print window select:
Color Handling: Photoshop Manages Colors
Printer Profile: QTR – Gray Lab
Rendering Intent: Relative colorimetric
Black Point Compensation: Off
Make sure the target is printed with the same exact settings you'll be using later for your images and without any color management applied during output. Save these settings as a preset, so they're easy to remember later.
Let the print dry for a few hours to make sure it reaches color stability.
Measure each patch and export the values in the QTR format. I'll be using a Datacolor Spyder3Print in this guide. It provides an option to export directly in QTR measurement format and is the cheapest measuring device available. This procedure varies depending on the spectrophotometer you'll be using. You can also manually insert the measured LAB values in the QTR-21-gray.txt template file, located in the QuadToneRIP folder.
Save the measurements file with the name you'll be using for your ICC profile. Keep it simple and descriptive: you'll want to remember what paper and settings this profile is for.
Drag and drop the measurements file on the QTR-Create-ICC-RGB droplet, located in the QuadToneRIP folder. It'll generate two files: an output text file, with the measurement analysis results, and an .icc file, which is your actual ICC profile. The output file will show a crude graphical representation of your measurements. Notice that the luminance curve is not perfectly flat and linear, as we'd want. This means my printer was not perfectly linear. The A and B channels represent the slight color tones caused by paper color, black ink tone, and spectrophotometer accuracy, which is worse on the near black tones. This color cast is imperceptible.
Why not use the QTR-Create-ICC droplet instead? Because grayscale ICC profiles are not supported by Lightroom. The RGB droplet creates a monochrome profile, but using a RGB color space, so Lightroom can load it. The end result is the same, but the RGB profile is more compatible. Depending on how you’ll be using the profiles, it might be useful to have both versions installed.
Copy the resulting profile to your system profiles folder.
Windows 7, Vista and XP
Note that the grayscale after profiling is more linear, almost a straight line. Besides soft proofing, which is handy, a linearized printer preserves better the subtle tonal separations throughout the scale. The end result is a slightly better and much more predictable print, even though the default driver output was pretty good, to begin with.
Always use the “Dark“ tone setting when printing on the Advanced Black and White mode of an Epson printer. It’s the most linear of all presets. Make sure to check it before printing, since the “Darker“ setting is selected by default.
Measurement file format
If you're using a different measuring device that can't export directly on the QTR format, such as the Colormuki, use this file as a template and fill in the measurements manually. Each line contains: line number, patch percentage, Lab L value, Lab A value and Lab B value.
Read more: Which is the most linear Epson ABW mode?