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A Call for Uniformity
By Roger Macie
There has been a great shift
from staff camera operators with company owned gear to owner-operator
videographers. Networks which had control of "their look" with staff
technicians, are now living with "the look" of independents. This, coupled
with the increase of magazine shows being shot with multiple cameras and the
general need for matched cameras, is causing a headache for independent
videographers.
Producers usually call crews with similar model cameras, in the hope of
achieving a matched look. When these cameras are put side by side, why is it
that they often look so different? Today's cameras are so stable and have
enough adjustments and range to easily match each other. The problem is that
these cameras are often set up by different technicians using different
charts, lighting, techniques and standards. In addition to that,
manufacturers have standards for set up that often differ between models.
There are three things that videographers can do to ensure that producers
are happy with their look. The first is to learn how to set up cameras to
match while out in the field, or to hire a video technician for each shoot.
Test charts, waveform and color monitors, along with time for setup, will be
needed. With today's budgets and time restraints, this would be difficult.
The second way is to have the cameras set up and matched prior to the shoot
by a qualified technician. Off-site camera setups, which are the least
expensive method, are usually impossible because of short notice and
scheduling problems. There is also a lack of available, local technicians.
The third, and best overall method, requires that your camera be set up to a
"uniform standard". Cameras set up with identical pedestal, gamma, flare,
matrix, detail and a few other parameters will closely match. For years, I
have been setting up all sorts of cameras. I have found that even cameras of
different manufacture, closely match the set up with the same parameters.
There are many other qualified, seasoned camera technicians, who similarly
set up cameras to look great, and at the same time, closely match each
other's. The problem is that there is no uniform standard that has been
adopted by the industry. This has forced each individual technician to adopt
his own standard.
Gamma setting, for example, involved much controversy. Gamma is the setting
of the gray, or mid-levels of the video signal, which is used to match the
corresponding mid levels of the picture monitors or television sets. A low
gamma setting makes pictures look darker and have more contrast, colors are
richer. A higher gamma brightens the picture and tends to wash it out. You
are probably familiar with gray scale chip charts that have a crossover on a
waveform monitor. This crossover corresponds to the gamma setting of a
camera. This particular crossover point varies with camera technicians.
Manufacturers have recommended values for this setting by sometimes
admitting that this is user preference.
Master black pedestal setting also varies between technicians. Some like it
set to 7.5 IRE which is called Set Up. Others prefer 10 IRE which keeps
blacks from clipping. Another important alignment is flare compensation,
which is through the lens black level adjustment. When adjusted properly,
true blacks in the picture remain the same as capped black, even when iris,
or picture is varied. If set improperly, black levels will rise or fall when
iris is opened and overall picture level will increase. If it did rise,
think of what would happen to the video if talent, for example, was shot
with a lot of blue sky in the background. The predominant color blue would
have its black level rise higher than the red and blue channels resulting in
an unbalance in black level. Changing the background to another color would
cause the color of dark regions to shift again.
The encoding of the color difference signals is performed by the camera's
matrix circuits. Each camera has a factory preset setting along with a
customer adjustable matrix that can be used to match colorimetry with other
cameras.
There are gray scale charts in use that have been available since the
development of color cameras. It has always been easy to match cameras to
look the same when shooting these charts. The problem, especially with
cameras of different manufacture and models, is that each cameras
colorimetry differs slightly. CCD blocks, lenses and different circuitry
vary among cameras. These differences can usually be compensated by what is
called the "matrix" adjustments. The matrix can be switched off, which is a
factory preset, or turned on and set to another setting which could be the
uniform standard.
A high-quality, standard color reference chart will be needed in order to
accurately set up a camera matrix. There is a chart available that was
developed in collaboration with the Canadian Broadcasting Corporation and
manufactured by DSC Laboratories of Ontario, Canada. This is not a typical
test chart, but a precision Optical Signal Generator (OSG).
With this chart and an agreed upon standard setting of gamma and matrix
settings, a true, uniform look can be achieved. Factory service centers,
networks and individual service technicians have begun to acquire these OSGs,
the only true color reference tool available.
This "uniform standard" should satisfy most end users of video./ Having a
camera set up at the highest, most acceptable standard, will result in
better looking video than the average setup today. Even cameras made by
different manufacturers set to the same standard will closely match.
Once a camera is set up to a uniform standard, each videographer will still
have the option of changing their camera's look. Adjustments using filters,
balancing through gels to get "the warm look", or even learning the basics
of some alignments themselves and resetting to the uniform standard before
the next multi-camera shoot will allow the videographer to change their
camera's look.
I am working with some key networks, retail companies, factory engineers,
and the DSC Company (Optical Signal Generator maker) in attempting to
develop a uniform standard, using an OSG, that broadcasters and end users
will be satisfied with. Hopefully, by the next newsletter, this uniform
standard will be available to you, as a camera owner, to adopt. When your
camera or camcorder goes in for service, just ask that your camera be set up
to this standard. |
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