More than three decades after he left his job in a traditional printing
shop, John Meyer still has the knack.
"I'd say that blouse is about 50 percent cyan,
35 percent magenta, and then, because it's got a bit of grey in it, about
10 percent black," he says, and
he's just about on target, still able to eyeball a color and break it down
into precise amounts of ink -- Cyan, Magenta, Yellow, Black.
That skill has
played an essential role in Meyer's career at HP, where he's helped engineer
a radical transformation in color printing from a costly, time-consuming
process handled exclusively by skilled professionals to today, when almost
anyone can quickly and easily print a good-quality color photo.
was part of the team that invented and developed HP's landmark thermal
inkjet color-printing technology, talks about some of the technical achievements
in HP Labs that made this transformation possible. Now director of the Hardcopy
Technologies Lab, Meyer also discusses some of his group's research into
the next frontiers of printing and imaging.
What we've done is engineer a radical transformation of the
world of color printing. The world that used to exist was a world
of craftsmen, skilled operators, expensive machines – it was a
In the past, if you wanted a color picture
on a piece of paper for, say, a magazine, you'd start with the
color original – a slide, artwork, color print, etc.
-- go through a process of color separation which,
after a lot of corrections and adjustments by skilled
people, another skilled person would convert it to
a Cyan, Magenta, Yellow and Black set of half-tone
films. Then you'd make a color proof -- a prediction
of the printed result.
Next was page layout and imposition, in which films must be registered
to each other with great precision. This required more skilled
Then you'd make the printing plates, involving more skilled
people. Finally, you'd go to the printing press. Extremely skilled
people were needed there -- the press operators who knew how
to control the offset press. Then you might put the materials through
a bindery. Finally, you've got your color picture.
was very closed. You, as the customer, got to maybe see the proof
and possibly do a press check.
If you had a negative, you could go to a photo lab. There you'd
work with lots of other skilled people, and they'd do a print for
you on photo paper. If you wanted something 8x10, it could get
expensive very fast. Again, it was all closed. You, the customer,
stood outside and waited for the result to appear. Your primary
function was to pay.
Today, we have a world where the customer can buy a camera, color
printer, PC – and can do something like this: Take a photograph.
Remove the memory card. Place it in a slot in the printer – and
All these highly skilled people have gone away. You can
print on photo paper or office paper. You can drop it into a document
and print that. We've put all this in the hands of consumers –for
less than $1,000.
The old printing world thought in terms of color in amounts of
ink. The reason for this is that offset presses specialize in putting
down a very controlled, thin film of ink. If you don't control
the ink density carefully, the image will look bad.
Because a press
is a tremendous investment, everything is driven toward making
the press efficient. It takes a lot of skill – for
example, a skilled color separator can look at a sweater or article
of clothing and say, this is 40 percent Cyan, 22 percent Magenta
and 5 percent Black, and be very, very accurate.
We've taken these
processes and opened them up. The customer is involved all the
way along. We've moved from densitometry, which is the measurement
of amounts of colorants, to colorimetry, measuring color based
on human perceptions, the way in which human beings see color.
That's more customer-centric.
This is what we've been doing in
I had an unusual combination of skills. I’d worked in traditional photo lithography.
But I also had a PhD in low-temperature physics. After my degree, when I went out looking for a job,
HP was looking someone who knew something about physics and about printing.
It was one of these splendid accidents of life. When I joined in 1979, inkjet
was just an idea. Early on, my work was nothing about color. It was all about
inkjet -- how to make the device survive, understanding the fundamental fluid
mechanics and thermal dynamics of thermal inkjet.
(In thermal inkjet printing, tiny resistors create heat, the ink vaporizes
and creates a bubble. As the bubble expands, droplets of ink are forced out
of the nozzle onto the paper. The collapse of the bubble retracts the meniscus,
pulling more ink into the print head from the cartridge.)
My work was to do
thermal modeling to understand what actually happened
when we turned the heater on -- what energy went into the surface and what
went into the substrate. Also to study the process of nucleation, which is
what happens when you heat a fluid to the point where it vaporizes and generates
The problem was that something in the process was damaging the resistor.
I was trying to understand how the damage mechanism worked and
how we might get around that.
We had very high thermal stress. We were heating something up very rapidly
and that generated stress on the materials.
I did an analysis to determine
if those stresses were actually the source of the damage, and what I
learned was that they were not. Instead, the bubble collapse -- a process
known as cavitation -- was the source of the problem.
The collapsing bubble
formed a microjet of fluid that impacted upon the resistor, almost like
a jack hammer. This was the source of the damage that eventually led to failure
of the entire resistor.
We solved the problem by creating a fluid flow architecture that moved the
bubble off the resister.
After we introduced thermal inkjet, we began
experimenting with the imaging capabilities of the device. Eventually,
we discoveed a mode of operating the device called multidrop, where you
could burst the nozzle at a very high frequency and send out up to 16
droplets at once.
That let you change the dot size, and if you could modulate
the dot size you could change the level of intensity of the color. What
is a picture but different levels of light to dark? At that point, we began
to look at printing black and white pictures, and while doing that, it became
evident that with simple steps we could make this a color printing device.
I went to a printing company in San Francisco and asked them to scan a
color transparency (slide film) for me and give me the halftones that they
would normally generate for an offset sheet-fed press.
to the process of printing dots of different sizes to mimic the impression
of different intensities of color. If the dots are spaced close enough
we do not see them and the impression we have is of varying levels of color
We then had to do a scanning process so we could get the
color photograph into Cyan, Magenta, Yellow, and Black (CMYK) – the colors
used for commercial printing. Once we had it in CMYK, the next task was
to covert the offset-style halftones to ones that we could print with our
multidrop ink jet mode.
The technique we employed is known as error diffusion. Instead of smoothly
varying the dot size, it distributes the printer dots according to the amount
of ink needed at a given location, while at the same time imposing a randomized,
or “scatter,” pattern that makes it hard to see the individual
The files were very large and had to be read from a tape drive, one block
of data at a time. The tape drive broke in the process -- it was not designed
for that type of data transfer. Once we made the conversions
we printed the CMYK halftones, one at a time, using a single
It was an incredibly painstaking process. We put the nozzle
on an x-y plotter (a grit wheel-based technology invented
in HP Labs) and printed out colors one at a time. We printed Yellow,
then put it back on and printed the Cyan, then the Magenta, then the Black – and
we printed out some of the first color pictures ever, right here
at HP Labs.
Gradually we began to get into all sorts of color
pictures. My life had come full circle. I had this background
as a color separator and suddenly, here I was applying it to
the world of inkjet. As time went on, we improved and improved,
and that eventually led to our work in digital photography.
Some time after we printed those first color pictures in the lab, Dick Hackborn
(an HP board member and veteran HP executive who led the
company's move into printing) told the inkjet business guys to "go do
That was a big decision. The PaintJet (an early HP inkjet) had these huge
dots, but we worked with it. It was 180 dpi -- you could count the dots --
but we did everything we could to make it work as well as possible.
didn't look didn't look like much in the beginning, but often things that
turn out good don't look like much in the beginning. That, to me, is one
of the fundamental things that HP Labs has got to be about.
HP drove the process. There’s hardly any company that matches us
in mastery of the color processes we’ve developed for our printers.
HP Labs played a huge role. We did the early work on how
to encode color for communication in computer systems. This led
us into colorimetry -- measurement of color based upon how peple
actually see colors. Ultimately, it is the combination of the human
eye and brain that produces the sensation which we all call color.
By encoding color data in human visual variables obtained via colorimetric
measurement, we moved from describing color in amounts of ink (CMYK)
to a method that relates directly to our visual perception. With
that as a foundation, we developed software called Architecture
for Color Imaging. What it did was take RGB (red-green-blue) data,
i.e. colorimetric data, and convert it -- through a series of algorithms
and processes and look-up tables -- to data that would drive an
Since we started from a basis of what
we would see, we could then convert the data for display on a computer
screen or output on a printer, and there would be a consistent appearance
between the two.
The thing that was remarkable was that there was no expert in the
process to do anything. It worked automatically. We took a lot of
what I knew, which was how to build colors by hand, and put it together
with a lot of color science and imaging science and created the
intelligent printer driver from that software program -- and that’s
been the basis for the drivers for all of our color printers since
We developed the fundamental algorithms that go into the cameras' image-processing
pipeline, the most recent of which is the adaptive-lighting technology that's
(Adaptive Lighting simulates the ability of the human eye to adjust for such
high-contrast scenes as a person standing in front of a window or children
playing in the snow. It lets point- and-shoot photographers easily replicate
what they see with their eyes regardless of lighting conditions.)
I used to deal with the problem of adaptive lighting when I was doing color
separation many years ago. I would get transparencies with very high contrast,
and I had to have an effective way of reducing the overall range so I could
produce a color separation suitable for printing on offset. In those days,
you could use a technology known as area masking. A photographer would call
it dodging and burning.
In the late 1990s I started a project in Labs called
the “high dynamic range
project” to find a solution for this. In the course of this, I came into
contact with the Retinex algorithm for adaptive lighting by Polaroid founder
Edwin Land. With quite a bit of work by the Labs team, engineers in HP's
Hardcopy Division – particularly senior color scientist Bob Sobol – we developed
the adaptive-lighting technology.
Yes, and then we use that information to take the very large brightness range
you see and fit it into the smaller brightness range that can be reproduced
on paper. At the same time, we bring into play all the experience
professional photographers have gained over the years.
The camera data is encoded in terms of what you see, i.e. colorimetric data.
Visually speaking, the dominant human visual sensation is lightness to darkness.
The second thing you’re aware of is hue. The third is saturation of colorfulness – the
intensity of a red sunset, for example.
What goes back to your brain are three signals. Red minus green, yellow minus
blue and the other is achromatic (without hue). The last signal, the achromatic
channel consumes 95% of the communication bandwidth or information carrying
capacity of the optic nerve. That means most of what you see is black and
We learned to derive colorimetric data from the electrical signals produced
by the sensors in cameras and scanners and then to build algorithms
that manipulate that information intelligently.
On top of all this, we’ve built algorithms that look
at image data and make intelligent decisions about it. These went into
HP cameras, scanners, printers and PCs.
Basically, it gave me the vision of automating the process of
color reproduction, taking the painstaking process of doing it manually and
using algorithms to automate that. We've succeeded in doing that. All the things
all those people used to do are buried in those algorithms.
For me, it's been a fabulous journey. As a color separator in the old world,
I used to dream of a system that could do all this.
It's enormously satisfying
from another point of view as well, because the process of color reproduction
has an artistic dimension. We're opening up the ability of individuals to
express themselves artistically. We have made photography much more accessible
to the consumer. It is quite easy to "play" with your
pictures and modify them to suit your taste.
Our group is in the midst of major initiatives in commercial digital printing,
where we are taking control of color to next level, the professional level.
It's called color management. We are advancing the technology we acquired by
purchasing Indigo N.V. to provide robust color printing solutions, from creation
of printed material to production on the printing press.
At the same time, we're
looking at advanced displays -- paper-like displays
with minimal power needs. Eventually these types of displays will be an important
part of the way people will see information, so we intend to be there.
to have a strong effort in digital photography, which is a fiercely competitive
business. We believe digital cameras are ultimately a lens, a filter and
a computer, and we intend to build on our expertise in computational image
processing to take advantage of that component.
We are exploring pervasive image
capture, wearable cameras, advanced imaging materials and we recently completed
some work in ultra low-cost paper handling and finishing.
We're also doing
advanced user studies to understand how people in separate locations might
use new capabilities to interact via images, or how extra dimensions such
as audio can enhance the overall photographic experience. Putting it another
way, understanding how digital imaging might improve people's lives. It's not
just a matter of putting technology in people's hands. It's understanding how
they will use it.