Advanced Colour Enhancer
GTH's ACE colour corrector looks
unsophisticated, but offers an easy
way to fix video colour problems
(GTH Note: This review naturally takes the videomaker's viewpoint.
However the ACE works with ANY video source and will also correct other
people's mistakes or equipment faults! Home Cinema owners wanting perfect
results also find it ideal.)
Here’s a question. Why, if you had the sophisticated video editing functions
provided in the latest computer-based systems would you need a little box
of tricks to perform colour correction functions? The answer - to save
One of the more odious problems connected with non-linear
video editing systems is the delay between finishing your edit and seeing
the results. The rendering time, during which the computer does all the
data-juggling required to take into account your cuts, effects and software-generated
titles, can run into hours, even for relatively short clips. Therefore,
the last thing you want to do is to add to the rendering time by making
small but global changes such as altering the colour balance.
This is where boxes like the GTH Electronics Advanced
Colour Enhancer comes in. Whether you are digitising video into your PC,
or outputting to tape, it's much easier to use this sort of box to do picture
correction than it is to do it in software and to accumulate rendering
time. Just as in the music recording process, where it makes more sense
to start with a good recording than to try to 'fix it in the mix,' it saves
a lot of time and trouble to correct problems or introduce certain special
effects before capturing video clips to the computer.
Perhaps the most obvious use for colour correction is for footage shot
using an incorrect colour balance setting. It's easy to forget when you
move from outdoors to indoors or vice-versa that the colour temperature
may change - unless the automatic colour balance functions on your camcorder
are very good, you might be landed with blue-tinged footage outdoors, or
orange-tinged footage under artificial light. Even if shooting exclusively
indoors or outdoors, changes in lighting may mean that the colour balance
of scenes may not match when you come to edit. The Advanced Colour Enhancer
can fix all this, and in such a way that minor changes can be made on-the-fly.
Though it looks a little home-made, the ACE is a sophisticated unit using
digital processing technology, and we're told that reliability is high
and the return rate remarkably low. Built using a brick-sized, plastic,
breadboard-style enclosure of the sort you might buy in Tandy, it's nonetheless
pretty sturdy and should survive the knocks of studio use. The double-sided
board seems to be well-enough designed, and the sockets adequately filtered.
We didn't experience any problems with outside interference, so you shouldn't
have any worries about placing it on your desktop near your monitor.
The knobs are of a decent size with centre markings.
The buttons are small but have a good positive feel. Around the back are
connection sockets for video signals and stereo/mono audio. The ACE has
no audio processing functions except a fader, but in any case it's handy
to have the loop-through sockets. There are audio, composite and S-video
inputs for the source machine and a selector switch to choose which video
input is used. There are outputs for VCR 1, and a Scart input/output for
VCR2. The video outputs are buffered and can be connected to two VCRs without
any level loss. There's also a connector for the external 9V power supply
which is provided.
On the front are 11 main knobs and 15 buttons, divided into five main areas.
Because there are settings on which the picture would disappear altogether,
it's good that there's a Bypass button to override all the processor's
In the Colour Controls section, Saturation enables
you to adjust colour level from zero (that is, b&w) to double normal
level, while the Balance control affects the colour balance of coloured
areas without changing overall white balance, and is useful for correcting
skin tones. The Shift function is for correcting the position of the colour
element of the picture, which can often slip out of sync with the luminance
element, especially on multiple generation tapes.
In the White Balance section, you have individual
controls for Red, Green and Blue colour levels - apart from correcting
colour balance faults, these controls can be used for special effects such
as creating a twilight hue or a sepia effect.
In the Video Controls section, Contrast and Brightness
can be adjusted, while in Special Effects you can alter picture sharpness.
There's also a Digitise function which gradually decreases the number of
colour and brightness levels in a picture, producing a 'paint' effect.
Of the push-buttons, the Invert Video and Invert
Colour buttons can be used separately or together to invert the brightness
or colour palette of the image - normally useful only for special effects
though it can also be used to copy photographic negatives to video. The
Pattern buttons are used separately to produce blank blue or red screens,
or in combination to produce the standard European colour bar test image.
These two buttons over-ride all others except Bypass.
Finally, there are Fade/Wipe functions. Though very
unsophisticated by the standards of non-linear digital effects software,
these simple wipe effects can sometimes be useful; the picture can be wiped
to black from the left, right, top or bottom (or any combination), or faded
to and from black under manual control, or automatically according to the
setting of the Speed knob, from around one to five seconds. With the Audio
button depressed, the sound is faded along with the video.
At £250 the ACE colour corrector is not exactly cheap. But, considering
the amount of time it might save you, it could be a very worthwhile investment.
Computer Video "RECOMMENDED", Overall Rating
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