Graphics Programs Reference
In-Depth Information
filing package can generate an ICC profile. Some packages, notably those
from GretagMacbeth, write the entire measured data into the resulting
ICC profile. This is useful should the saved measured data file get lost or
should a user wish to see the measured data directly from within the ICC
profile. This allows the GretagMacbeth products to build a new or mod-
ified profile without needing to access the measured data file. The main
downside is the profiles can be larger in file size due to this added data,
which is stored in private tags (see Chapter 8 for utilities that allow you
to access this kind of data from an existing profile).
Sidebar
Spectral Data and Data Files:
Although a Spectrophotometer is able to record spectral data,
most software packages save out the measurements in CIELAB. This is fine for building output
profiles, but having spectral data provides a host of useful options. One use of spectral data
used to its fullest in a profile-building package is to automatically detect and account for optical
brighteners (discussed later). If a user can measure the illuminant, it's possible to build an output
profile that uses this data to compensate for metamerism when a print is placed under that
illuminant. Since most ICC output profiles are built for Standard Illuminant D50, having the
spectral data of the illuminant under which the print will be viewed is a very useful feature.
With an Eye-One Pro Spectrophotometer and its ambient light head, I can measure the light
box I plan to view my prints under or go into an art gallery and measure the illuminant under
which I plan to show my prints. Then with that data, I can build an output profile for those
conditions instead of assuming a Standard Illuminant of D50 (see Fig. 6-19).
ProfileMaker Pro is a package that allows the use of spectral data to accomplish many of
the tasks just mentioned. To build an output profile based on a specific viewing condition, I
would use is the Eye-One Pro and the Eye-One Share utility to measure the illuminant. Once
the ambient head is placed on the Eye-One Pro, I click the measure button and the data is
recorded in Eye-One Share as seen in Fig. 6-18. That data is saved in a format called CxF. I can
then load or drag and drop the light source data into ProfileMaker Pro, after which it can be
selected in the
Viewing Light Source
pop-up menu. Data files composed of spectral data are
usually much larger than their corresponding CIELAB data files. However this information is infi-
nitely more useful when used with a software package that can take advantage of this type of
data.
Optical Brighteners
Some papers we use in our output devices have what are known as
optical brighteners. Optical brighteners are fluorescent compounds found
in materials that absorb invisible ultraviolet light and reemit it as visible
light (usually in the blue part of the spectrum), producing a brighter
appearance from that material than really exists. Our eyes are unable to
detect these optical brighteners but Spectrophotometers recognize this
