| 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.
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. From: George Hammond Lithco
Weekly Word Angela Wolf
of Ihara U.S., Inc, authored this Lithco Weekly Word.
A
reply to a customer’s inquiry for low cost, inexpensive
densitometer Keith Lee @ Ihara To: George Johnson Hello George, Here is my reply to your customer: First and foremost, there are many different transmission
densitometers in the market. They range from $700.00 to
$2,400.00 retail. The surprising thing is that they all have
the identical specifications -- pretty much all of them claim
that they can read up to 6.00 density. Therefore, how is a
customer to distinguish one model to another? The most important thing to look for in a transmission
densitometer is the ability to read linearly up to 6.0
density. What this means is that just because your machine
reads 5.5 density does not mean it is accurate. For example,
if a bath scale shows that I am 300 lbs., am I really 300
lbs.? You need to make sure your scale is accurate. In the
case of the transmission densitometer, it is the same!
Accuracy, accuracy & accuracy! Next, we need to understand what density means. Density of 1.00 = 10% transmission of light through the
film As you can see from above, a machine that can read 5.00
density has to be fairly accurate. This means that this
machine can detect 0.001% light through the film. Agfa, Kodak,
Polychrome and Fuji requires most newer image setters to burn
their film between 5.0 - 5.4 density. Therefore, a customer
really needs to be careful in selecting a transmission
densitometer. Now that we are clear with what density means, we need to
know how we can compare one densitometer to another. In most
cases, almost all transmission densitometers can read 3.0
density accurately. 1. Take a film that is about 3.0 density and measure it
with your densitometer. For example, your reading may be
"3.20 Density." 2. Take another film that is about 2.5 density and measure
it with your densitometer. For example, your reading may be
"2.30 Density." 3. Now, combine the two films together and measure it with
our densitometer. A very good transmission densitometer will
read "5.50 Density" using this example. This is a
simple test to check the Linearity of the machine. In most of
the inexpensive machines, the reading from the above test may
read "5.20 Density." The clearly shows that the
inexpensive machines cannot read up to 5.50 density
accurately. 4. Any customer considering buy a transmission densitometer
should look for the lowest priced machine that can pass this
test. Enough said, our T500 transmission densitometer is to
absolute lowest priced unit that can pass this test. In
addition, many of the models that were mentioned by your
customers are simply "junk!" George, our T500 transmission densitometer retails for
$1,295.00. That is a $1,000.00 less than a comparable unit in
performance. Thanks for the opportunity! Have a great weekend... Keith Lee
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