Graphics Programs Reference
In-Depth Information
the ECI2002. Some Spectrophotometers need a scrambled target so
the instrument and software can differentiate the beginning and end of
a row of patches. This usually is seen in handheld scanning Spectropho-
tometers like the Eye-One Pro, PULSE, and Spectrocam. Other than the
visual appearance, scrambled and nonscrambled ECI2002 targets are the
same. For RGB targets, there are no standards so each profiling package
will provide any number of patch targets, from as few as 45 to over
10,000.
We might assume that more patches are better when it comes time
to select a target, but there is a point of diminishing return. In a perfect
world, we would output one patch for every possible color that needs to
be measured. Once you begin to consider the task of measuring 16.7
million colors to build an RGB output profile, then consider that the final
size of the resulting profile would be larger than many image files, it
becomes clear that a subsample of colors is the only viable option. I've
built printer profiles for devices using as few as 45 patches and as many
as 10,500 patches. Based on this I would recommend most users look at
RGB targets that contain about 800 to 1500 patches. Fewer samples, by
and large, do affect the quality of a printer profile. Over 1500 and the
improvements seen are less noticeable, although improvements can be
detected for some printers. Progressively more patches mean you'll spend
more time to measure the target and have to output more targets pages.
If the software package you are using provides an option of patches, start
with a target in the ranges just mentioned. If increased quality is neces-
sary, you can try to build a profile with more patches. Avoid building
profiles with small samples (less than 300), as the results are usually poor,
certainly with printers that are nonlinear. For CMYK output profiles, the
1485 patch ECI2002 is ideal.
When sending a target to the printer, it can be critical that the patch
sizes remain fixed, depending on the Spectrophotometer measuring the
patches. Most Auto-Spectrophotometers, like the DTP-41 and iCColor,
will reject a target if the patches are either too large or too small result-
ing from the user or print driver resizing the target page. Many of the
targets generated or supplied by the host application are small, low-
resolution TIFF files. A user may need to resample the target to match
the native resolution of the printer. For example, when I print to my Fuji
Pictrography 4500, the largest paper size is 12 ¥ 18 inches and the only
output resolutions the printer supports are 266 dpi and 400 dpi. If I have
to print a target that is 12 inches at 72 dpi, I have to resample the target
to one of the native output resolutions, otherwise the printer will scale
the output. The patches will be the incorrect size.
I use Photoshop's Image Size dialog and set the resample algorithm to
Nearest Neighbor since this will produce clean upsizing of the solid patches
as seen in Fig. 6-15. Most print drivers will inspect an image file and
simply print it at the size indicated, ignoring the file's resolution. If I send
the same target just mentioned to my Epson 2200, the driver will see that
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