Nowadays, commercially available digital cameras are
widely used to measure a color 1, 2.The purpose of this document is to document
the practical assignment for an imaging measurement with an imaging setup characterized
or calibrated for the measurement task. During this measurement, few aspects
can be understood:
a) Measuring equipment
b) Object that we need to measure
c) Describing the purpose what kind
characteristics we have found.
Every device depends on different color
models to display color. Input devices – your camera and or computer output
devices (monitors or screens) – use the additive color model to display color.
They start with darkness and add red, green, and blue light to create a
spectrum of colors. Printers, on the other hand, use the subtractive color
model. They start with white and using opposing colors – cyan, magenta, and
yellow – to subtract color 4.
In our methods, we have used the standard color chart; the X-rite Color-Checker
24-color “normal” version was used. Mostly, the digital cameras are
being used in RAW mode and after that we need to convert these RAW files to an
uncompressed 24-bit format with the help 8-bit on each channel RGBs color space
by computer programs which is normally provided by manufacturers. The RGBs
color space was defined by the International Electro-technical Commission (IEC)
adopted the RGBs because it is one of the most common color spaces in the
imaging products and almost all digital cameras on the market have the RGBs
color space mode. You can see the digital cameras list used in the measurements
can be seen in Table given below:
Manufacturer and model
of the image correction method applied for each camera is as follows:
1) Taking the uniform photo or image
2) Take photos of a sample with the
ColorChecker 24-color chart (size: 60 x 90 mm) and 140 colors under the same
illumination condition of Step 1. As a sample, another ColorChecker chart was
3) Perform the shading corrections for
photos of Step 2 using the coefficients derived in step 1.
4) Calculating the color correction
Apply the color correction values derive at Step 4 to all pixels of photos of
the step 5, the color corrected image files in the RGBs space are obtained.
Conversion equations between sRGB and the tristimulus values are defined in
Ref.3. Then, the color data can be converted to any color space attributes.
We converted the sample data to the CIE 1976 L*a*b* color space for discussion.