A group of students and staff members at Clemson University have created a study using accurate, and low-cost sensor technology to collect soil color data. The objective of this study was to develop a mobile application that would enable users to create their own soils database consisting of GPS location and soil color data gathered using the application with the Nix Pro. The content below will discuss background knowledge on this study, and show how the Nix Pro Color Sensor has been used to benefit the research and development of this mobile application. All original data and further details from this study can be read, and found at: Geoderma.
How connected color measurement devices are changing the way we track color trends and color quality
Throughout history, color has been the domain of the artists and creative people in our society, like painters, architects, and designers. Aside from a well-developed understanding of color theory, decisions about color are made largely on intuition or taste. However, in today’s world, color decisions can have economic consequences, not just aesthetic ones.
For example, when you need to match a paint color on your wall, verify that brochures have your company colors correct, or even determine if an avocado is ripe or not, using intuition instead of data can be costly as well as unsightly. And if you’re a fruit producer that exports thousands of pounds of avocados on a weekly basis, misjudging the ripeness of your crop can have a serious impact on your bottom line.
The NIX Pro Color Sensor is able to convert between any physical or digital color system in the world. Here’s a look at the HSL color system, which is used in image editing software.
Introduction to the HSL Color System
One of the most common ways to communicate color is through visual systems like charts, where each color has its own unique set of co-ordinates. For example, the RGB color system can be arranged as a cube with 255 discrete points per side:
Although a cube may seem simple, it is actually fairly challenging to visualize the differences between colors. In addition, identifying complementary colors is neither easy nor intuitive. The Hue, Saturation, Lightness system was developed decades ago as a way to evolve the RGB color system by making it easier to visualize.
How does HSL Color Work?
In HSL, the Hue determines what color of the rainbow something is. It’s represented in 360 degrees, like a traditional color wheel. One of the main advantages of HSL over RGB color is that complementary colors are located across from one another, which makes the whole system very intuitive.
The distance from the middle of the color wheel is called the ‘Saturation’, or how much of a given hue is present. Looking closely at the color wheel above, it is apparent that the color becomes brighter and more vivid as one travels from the center of the circle to the edge.
The Lightness value of an HSL color is in a third dimension, which actually makes the HSL system a cylinder:
As shown in the above diagram, the ‘Lightness’ of a color is a gradient between black and white, where the ‘bottom’ of the cylinder is a total black, and the ‘top’ of the cylinder is totally white.
Using HSL Color
People familiar with image editing programs might be more familiar with HSL than they realize. The main advantage of HSL is that it makes it easy to select a color quickly – otherwise, users would have to painstakingly adjust and tweak RGB sliders until they get the color just right.
Disadvantages of the HSL Color System
Although the HSL system is convenient to use, it isn’t particularly representative of how the human eye actually views color – this means it doesn’t translate well into other systems that have more of a scientific basis.
Charles Poynton, a digital video expert, explained the problems quite well:
HSB and HLS were developed to specify numerical Hue, Saturation and Brightness (or Hue, Lightness and Saturation) in an age when users had to specify colors numerically. The usual formulations of HSB and HLS are ﬂawed with respect to the properties of color vision. Now that users can choose colors visually, or choose colors related to other media … or use perceptually-based systems like L*u*v* and L*a*b*, HSB and HLS should be abandoned.
The NIX Pro Color Sensor is able to convert between any physical or digital color system in the world. Here’s a look at the CMYK color system, which is used in printers worldwide.
Introduction to CMYK Color
The CMYK color model, also known as process color, was first popularized at the turn of the 20th century. After extensive experimentation in the 1800’s, it was found that cyan, magenta, and yellow inks provided the largest possible set of unique colors in printed media. Black ink, (the k stands for key) was added to the mix because it could not be accurately reproduced using the other three inks.
How does CMYK Color Work?
The CMYK color model is based off of the fact that surfaces appear to be certain colors because of the wavelengths of light they absorb and reflect. For example, things that appear to be red will only reflect red light. Objects that appear to be white will reflect all wavelengths of light, and objects that appear black absorb all wavelengths (which is why you should avoid wearing black in the summer to stay cool).
As a subtractive color system, CMYK color takes advantage of this phenomenon by depositing inks on a surface in order to selectively absorb certain colors of light. The light that isn’t absorbed by the inks is reflected into an observer’s eye, which results in them seeing the intended color.
As shown in this example from LCI Paper, different colors of inks are printed onto a surface in dots and then layered in order to produce the desired color. This is called ‘half-toning’, and conserves ink while creating the appearance of a solid color provided the dots are small enough.
The size and spacing of dots can be altered to produce the overall visible color. The dots are also printed at angles to each other in order to avoid creating unintentional patterns which could be visible to the user (called Moiré patterns).
How Do You Use CMYK Color?
Unlike RGB color, which is used in screens and digital display technology, CMYK color was created for printed materials. Where RGB color has three channels for red, green, and blue, CMYK color has four channels for cyan, magenta, yellow, and key (black). Each of these channels is measured from 0% to 100%, and will tell the printer the relative density of each ink that is required. Here’s an example from our Real Color gallery:
CMYK (Dark Green): 70 . 17 . 64 . 1
CMYK (Light Green): 27 . 19 . 100 .0
CMYK vs. RGB in Photoshop
Some programs (like Adobe Photoshop) will automatically display in RGB color spaces, and so it may be necessary to change the color profile of the image if you are intending on using it in print.
It is also important to be aware that the RGB color space contains more colors than the CMYK color space. This means that some special care will need to be taken when converting files from RGB to CMYK, as some of the colors can appear dulled.
K=100 Black vs. “True” Black
Although it might seem counter-intuitive, using 100% black ink in process color (CMYK: 0 . 0 . 0 . 100) is not the darkest black possible in the color space. So-called “Rich Black” or “Photoshop Black” (CMYK: 75 . 68 . 67 . 90) is a much deeper black because it absorbs more light.
The reason that “Photoshop Black” isn’t often used in print is that the sheer amount of ink can rip lower quality paper like newsprint. In addition, for details like text, using too much ink can create a muddy appearance, which will affect readability.
For large areas that will be colored black, small amounts of other inks can be added to K = 100% to create a rich black without oversaturating the paper with ink. Some examples include:
Cool Black: 60 . 0 . 0 . 100
Warm Black: 0 . 60 . 30 . 100
Designer Black: 70 . 50 . 30 . 100
Rich Black: 75 . 68 . 67 . 90
The NIX Pro Color Sensor is able to convert between any physical or digital color system in the world. Here’s a look at the RGB color system, which is used in electronics and display technologies around the world.
Introduction to RGB Color
The RGB color system is one of the most well-known color systems in the world, and perhaps the most ubiquitous. As an additive color system, it combines red, green, and blue light to create the colors we see on our TV screens, computer monitors, and smartphones.
Although used extensively in modern technology, RGB color has been in existence since the mid-1800’s, and was originally based on theories developed by physicists such as Thomas Young, Hermann Helmholtz, and James Maxwell.
Image Source: Wikipedia
Some early examples of RGB color in use were in vintage photographs (the above photo was taken in 1861) and cathode ray tubes. In modern technology, LCD displays, plasma displays, and Light Emitting Diodes are also configured to display RGB color.
How does RGB Color Work?
The parts of the human eye that are responsible for color perception are called cone cells or photoreceptors. RGB is called an additive color system because the combinations of red, green, and blue light create the colors that we perceive by stimulating the different types of cone cells simultaneously.
Image Source: SpaceTelescope.org
As shown above, the combinations of red, green, and blue light will cause us to perceive different colors. For example, a combination of red and green light will appear to be yellow, while blue and green light will appear to be cyan. Red and blue light will appear magenta, and a combination of all three will appear to be white.
How Do You Use RGB Color?
RGB color is best suited for on-screen applications, such as graphic design. Each color channel is expressed from 0 (least saturated) to 255 (most saturated). This means that 16,777,216 different colors can be represented in the RGB color space.
Advantages of RGB Color
Almost every well-known application is compatible with RGB, such as Microsoft Office, Adobe Creative Suite (InDesign, Photoshop, etc.), and other digital editors.
Drawbacks of RGB Color
One of the major limitations of the RGB color system is that it doesn’t translate well to print, which uses the CMYK system. This has led to a great deal of frustration when people print out documents from Microsoft Office, only to have them turn out to be the wrong color.
In addition, different devices often use different types of LEDS. This means that the same color co-ordinates do not display consistently across smartphones, TV screens, or even monitors. This can present some unique problems for professionals who work with precise digital color, from special effects to graphic or print design.
The vast majority of the human population is extremely sensitive to differences and inconsistencies in color. Intuitively, we are able to sense when a color is ‘off’. However, when it comes to scientific equipment and color sensors like the NIX Pro, it becomes necessary to determine the accuracy in mathematical terms.
Color can be precisely described in several different co-ordinate systems, such as XYZ, RGB, CYMK, or L*a*b*. In these systems, different values are assigned to variables like L*, a*, and b*.
The L*a*b* Color Space. Source: w-enter.com
In particular, the L*a*b* system can be plotted as a sphere that contains hundreds of thousands of different colors. Each color has its own unique point within the sphere.
The “Delta-E” Measurement
In order to calculate the difference between two colors within the L*a*b* system, all you need to do is calculate the distance between their respective points in the sphere. From a mathematical standpoint, this is essentially trigonometry (here’s the Wikipedia article for the nerds out there).
Measuring the distance between A and B. Source: http://pengantar-warna.blogspot.ca/
The distance between two colors is known as the Delta-E, and is an industry standard that is overseen by the International Commission on Illumination. From a practical perspective, the average human eye cannot detect any color differences with a Delta-E value of 3 or less, and an exceptionally trained and sensitive human eye will only be able to perceive color differences with a Delta-E of 1 or above.
What Does This Actually Look Like?
To give you an idea of how different Delta-E values actually appear in real-life, we created the following sets of color swatches. Note that the quality of your monitor or smartphone might affect your ability to perceive these colors properly.
With a Delta-E this large, the two colors are clearly different from one another.
Even with a relatively large Delta-E of 5.65, these two color swatches aren’t incredibly different from one another.
Delta-E values of around 3 represent the limit of most people’s perception. It may take a second glance to realize that these are two different colors.
To the average person, these two colors will appear to be the same. Only a few people reading this will be able to detect any difference.
Detecting Color with the Nix Pro
The Nix Pro Color Sensor is capable of comparing between color samples to determine the Delta-E difference of two colors. This can be used on production lines, print proofs, and industrial processes to ensure color accuracy quickly, cheaply, and effectively.