首頁 ﹥ FAQs > 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
!