Home ﹥ Custom Page > FAQ - Camera DCC Filter > ☉ What's wrong with my camera AWB?
☉ Why does the Auto White Balance (AWB) of the most advanced camera shoot the photos with wrong colors from time to time?
Except for a
few of the early advanced SLR cameras equipped with an independent
unshaded external white filter for its AWB, such as Nikon D2X,
etc., all the cameras, including DSLR camera, EVIL camera, digital
cameras, video recorders, smartphones, tablet PC and computer video
cam, use the logic calculus AWB
(Auto White Balance) to deduce the camera white balance value
instead of getting the actual white balance value of the framed
scene with a real optical filter to do this
job.
Every camera /
mobile phone manufacturer has its own unique formula and weighted
white color balance calculation methods under the unopened black
case operation. That leads to very different color distortion
photo at different scenes. Take all the latest camera models of all
brands to aim at the same scene and shoot at the same time, you
would notice that the colors of
each of these captured photos are quite different from each other
while the real life overall color of the scene is one only under
that particular lighting. Thus, you can easily see
how serious calculation errors may
occur in the the AWB (Auto White Balance) systems of each
camera.
The basic
concept of white balance is that white can be restored to white no
matter under what light the sources are. The function of the so-called AWB (Auto White
Balance) is to restore all the colors under color cast lighting to
the colors under the standard illumination automatically.
International Commission on Illumination CIE defined the standard
illumination is D65 light source with the color temperature of
6500K. The Color Calibration restoration definition is to restore
for true color of the rendering scene. Color is the color
temperature of the light itself. While the purpose of camera AWB is
to correct all the color cast caused by the light source.
This is the main reason many cameras capture the photo images in
wrong tone of noon during the evening.
There are several camera AWB (Auto White Balance) simulation
algorithms:
Grayscale World Assumption
Grayscale World Theory: according
to this theory when there is enough color change with one photo,
its R, G, B value of all components tends to a status of balance (
even if the numerical value of the three: R, G, B is equal, in
other words should be the type of color: black, white of gray.) As
regards the white balance, this theory has a wide range of
application. One distinguishing feature is that it can use much
more image information to make a judgment but when it is used with
an image that is composed by one color (single color image), there
are some problems that may appear.
Standard Deviation Gray World
Assumption
Standard Deviation Gray World
Assumption is an algorithm directed towards improving the
above-mentioned assumption. It works on the principle of dividing
one image in several parts (blocks), then performs a statistical
analysis on each part (block) of the image, looks inside its color
richness, more proportions on the weighted color while less
proportions on fewer colors to reach a final average summation.
Then, the RGB value would be modified according to the relatively
accurate summation.
Perfect Reflector
Assumption
Perfect Reflector Assumption: The
point of the maximum brightness of the image is the white point. It
assumes that the biggest Y value is the white color of the YCbCr
space and uses it to revise the colors of the entire image. It is
characterized by considering only that part of the brightest colors
and is completed on the contrary to the above Gray World
Assumption. This assumption might achieve better results when
dealing with particular monotone color image. However, it may have
the color cast or overkill circumstances when faced with the color
rich pictures since the brightest point is not necessarily the
white color.
All the known or undocumented camera AWB logic
calculus would encounter occasional or frequent computing errors to
shoot out with color inaccuracy photos due to environmental
complexity or its logical calculus imperfection.
They are extremely unreliable to
shoot for a color correct photo. Of course, every
camera manufacturers would claim that they have made significant
improvements towards colors and AWB on their latest model of the
cameral or video CAM when it was announced. The truth is that this
kind of claims have been the same over the last two decades.
In spite of improvements through
camera from one generation to the next generation, its AWB function
is still unreliable up to this day. Until the camera
manufacturers adopt our patented technology of “built-in or
external white balance filter device” in the next generation of new
camera, this color inaccuracy problem on every new camera AWB
phenomena would be continued.
Until then, “RAYNAULD™ Directivity Color Calibration
Filter” is the best and only solution to shoot for an almost
perfect color photo anytime anywhere !