| Cinema Cynergy March 2001
Video Calibration of Your Home-Theater System
Have you ever noticed when you go to the audio/video store
and look at that huge wall full of televisions that the picture on each one of them looks
just a little bit different, and that a few look very different from most of the
rest? This occurs because the televisions in the store probably have their picture
controls set to the factory presets, and each manufacturer seems to have a slightly
different idea of what those should be. Manufacturers realize that their televisions on
display are competing for your attention. Their factory presets are designed to grab your
attention with a bright and colorful picture and not necessarily to properly and
accurately display video information. Thus your television, as it comes from the factory,
will not be properly setup for accurate viewing of a high-resolution video source such as
a DVD. While the picture might appear punchy and bright, it will lack resolution and
detail when compared to the picture of a properly calibrated television set.
Professional calibration is available from many specialty
dealers with Imaging Science Foundation (ISF)-certified technicians who use professional
instruments to measure color accuracy. These technicians can make any television perform
to its maximum potential by making adjustments that should not be attempted by untrained
individuals. However, there are test DVDs that allow consumers to manipulate the
user-accessible controls on televisions to get the most from video-display devices. This
makes much more sense for the typical user than hiring a professional technician to
calibrate their system.
What you can expect when calibrating a video-display
device
The picture of a properly calibrated set might look dim and
unexciting at first, but after extended viewing, it will become apparent that there is
much more detail and higher resolution. Also, do not expect your television to look its
best in high light conditions. Video displays always look their best when viewed in dark
rooms. Thus you should calibrate your television under the same lighting conditions that
are used while watching DVDs, which should be as dark as possible.
Most, if not all, sets are incapable of displaying a
perfectly accurate picture even when calibrated by a professional technician due to
limitations in their designs. Even though you will not be able to perfectly calibrate your
television using a test DVD, the picture quality will still be greatly improved after
using this procedure.
Video calibration, while not a trivial process, is still
relatively straightforward and simple if you follow the step-by-step instructions provided
on the test DVD. However, it is more complicated and time consuming than the audio
calibration procedure that was described in last month’s Cinema Cynergy column.
Depending on how proficient you are at it and how finicky you are, it could take anywhere
from a few minutes to a half an hour or more when you go through the step-by-step
instructions for each test pattern.
What you need to know to calibrate your television
Each test DVD contains instructions and video test patterns
to help you properly set the following controls on your television:
- White Level (Contrast, Picture)
- Black Level (Brightness)
- Sharpness (Detail, Peaking)
- Saturation (Color, Chroma)
- Hue (Tint)
I will not attempt to describe how to use the various video
calibration test patterns provided on these test DVDs because each one will vary slightly
from disc to disc and they are best explained in the DVD.
Be sure that you warm-up your television for about a half
an hour before attempting to set these controls so that the electronics in your television
are at normal operating temperatures; otherwise, the levels may differ. Remember to dim
the lights down to the usual level at which you watch DVDs. Prior to calibrating your set
for the first time, it's a good idea to watch the entire test DVD at least once to get an
idea of how all of the test patterns and controls work and relate to one another. After
you have calibrated your set a few times and are familiar with the procedure, you can skip
directly to the test patterns and forgo the introductions and instructions. It is
recommended that you calibrate your video display anywhere from once a month to once every
few months.
One thing that the test DVDs do not seem to mention is that
most televisions have a user selectable color temperature setting. Properly calibrated
sets should have the color temperature set to 6500K, so you just pick the corresponding
setting, right? Well, the problem is that most manufacturers label these three settings as
"Cool," "Medium," and "Warm," or something similar, without
telling you what the actual values are.
According to Home Theater & Sound technical
guru, Doug Blackburn, the actual values of these settings vary widely from manufacturer to
manufacturer with many televisions not having a single setting that properly matches the
6500K level. Some high-quality sets (ones that adhere to the 6500K color temperature
standard) will use the middle setting for 6500K, but most other sets should be set to the
warmest (the least blue-looking) setting, which will often not correspond to 6500K either
but is usually the closest of the three.
A curious side note is that some televisions will disable
the hue/tint control when connected via the component video input. This will severely
limit the utility of calibration and may mean that a better picture can be obtained by
utilizing an S-video input rather than component video input.
Fine tunin’
Because almost no consumer television set can be calibrated
to perfectly display video information, the picture will always be compromised in some
way. Depending on your preferences, these compromises can be adjusted to make the picture
more subjectively suitable to your tastes. For instance, even though the brightness and
contrast of your television may be set as accurately as possible, the set may still have
difficulty holding blacks when the average picture level is quite high. In this case,
black will sometimes appear as gray. If this happens, you may want to decrease the
brightness control and also adjust the contrast accordingly. Deficiencies in your
set’s color decoder may also result in a picture that is still too red or too green
after calibration. Some subjective manipulation of the color and tint controls may be
required to achieve the picture that is most desirable to you.
Where to find the test DVDs
 The two DVDs that I recommend to users
for calibrating their video displays are Video Essentials and the Avia Guide to
Home Theater. Both of these offer a complete suite of video and audio test signals
with explanations as well as instructions on how to use them. I strongly urge anyone who
is serious about performing video and audio calibration tests on their home-theater system
to purchase one of these two DVDs. Although Avia is more comprehensive and easier
to use than Video Essentials, both will do the job quite well. There is also a DVD
titled The Ultimate DVD, although not as highly recommended, that provides all of
the necessary tests for audio and video calibration. DVDs featuring the THX Optimode test
signals can also be used, but unlike the aforementioned discs, they lack the blue filter
that is required to properly set the color and tint controls, which severely limits their
usefulness.
If you do not already own one of these test DVDs, the Avia
disc is worth the premium in price over Video Essentials because of its ease of use
and more comprehensive test patterns. For instance, the test for contrast, "Needle
Pulses and Steps," is combined on one test pattern so you do not have to switch back
and forth between two different screens. Also, the test pattern used to set the brightness
control does not rely on the DVD player’s ability to display blacker than black
signals. Similarly, the other test patterns for sharpness, color, and tint in Avia
are all easier to use than those in Video Essentials. There are also additional
test patterns including one for estimating the accuracy of the television’s color
decoder.
Although Avia is superior to Video Essentials,
it is probably not worth going out and purchasing it if you already own Video
Essentials. For those that already have The Ultimate DVD, you may consider
purchasing one of the other two discs, but you can get by without them.
Just do it!
If you have a multi-kilobuck, state-of-the-art display
device, then nothing can take the place of professional video calibration. However, if
like most people, you own a consumer-grade direct-view or rear-projection display device
(myself included), then investing in a test DVD and the time to learn how to use it is a
very cost-effective upgrade. Even something such as an inexpensive 27" direct-view
set that has been calibrated using one of these discs will look stunning and film-like
when playing back DVDs.
...Roger Kanno
roger@hometheatersound.com
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