Densitometry
Made Simple – Ihara Densitometers
In a perfect world, you would
be able to create artwork, output a film positive, expose a
plate, and print the graphic with no loss of image
integrity. Unfortunately, the reality is that something
usually gets lost when the image progresses from one stage
to the next. Dots become larger or smaller. Colors in the
printed image don't match the final intent. However, you can
identify and control these problems by using densitometers,
a solution that's neither complicated nor expensive.
IHARA
R-Series Color Reflection Densitometers can
aid printers in several areas of the production process.
Reflection models are used to monitor printed images for
color density, dot area, dot gain, ink trap, print contrast,
hue error, and grayness, among others. Although a reflection
densitometer does not measure color per se, it provides data
you need to make accurate comparisons and color corrections.
With this device, you have the advantage of relying on
quantified base readings, rather than on subjective visual
inspections.
Any one of Ihara’s R-Series Color Reflection densitometers
(Models R710, R720 and
R730) provide an automatic density reading of the
predominant color (CMYK), along with a breakdown of the
remaining three colors for comparative purposes. These units
are menu-driven and automatically calculate color reflection
density and density difference. Many printers are content
with these basics from a densitometer; however, many also
are looking for help in aiding with dot size and dot gain.
Changes in dot size are probably the most common reasons for
inaccurate color. Any alterations to dot size that occur in
prepress or production can have devastating effects to
images. It's important to monitor dot size and recognize and
correct any deviations you discover. For this reason, dot
area and dot gain are included with the R720
Color Reflection Model. Dot gain occurs when wet
ink comes in contact with paper. As the halftone dots are
applied to the paper, the wet ink spreads, causing the dots
to increase in size and halftones to appear darker. This is
common to any printing job; however, with your dot gain
readings you can keep your dot gain level consistent. This
densitometer will provide information about the percent dot
area and will allow you to measure the coverage of the
printed image, then will automatically compare these
readings and display dot gain.
Finally, if you are looking
for that densitometer to do everything, then you will be
interested in Ihara’s R730
Color Reflection Model. The R730 offers you, in
addition to the R720 functions: Ink Trap, Print Contrast,
Hue Error, Grayness, Saturation, Cast, Brightness, and Dot
Analysis. Each one of these functions helps contribute to
better quality control during the printing process.
Your Hue Error value allows
the comparison of two printed inks in regard to their hue
shade. They allow a rough comparison of inks from different
manufacturers or between different deliveries of ink from
the same supplier.
The grayness reading shows
how "dirty" the ink is. This aids in monitoring
the quality of your inks and to check for contamination,
during your press run.
Ink trap is the ability of a
wet ink film to grasp and hold a second film that is printed
over it. If it doesn't stick, the results will be
disappointing. Ideally, you hope to trap one ink with
another as efficiently as you trap that ink with paper. For
this reason, we offer this function to you on our R730. By
monitoring your trap values, you can avoid poor trapping,
which could result in color shifts. We evaluate or measure
trap in terms of percentage. A high percentage is
"good" because it gives the desired color. A low
percentage, (typically, below 65%), which gives uneven
color, is considered "poor".
A print should have as high a
contrast as possible, However, the increase in ink, is
desirable only up to a certain point before it becomes
plugged up and you no longer have dots. With the Print
Contrast function, displaying contrast values as they
increase, and then the point at which it begins to decrease,
this allows you to realize your maximum density for maximum
contrast level.
I know printers find it
difficult to justify the money for a densitometer. What you
have to consider, is that if you do not have to rerun just
one job, you have just paid for your densitometer. I hope
that I have helped in explaining the value to having a
densitometer in a print shop.
If you still feel a little
uneasy, test out an evaluation unit, and see for yourself
how your printing jobs can become more worry free.
Ask about our 14-day trail
and evaluation program.
