Paint Dye RYB Color Meter

Finally there is a Android(TM) Color Meter that measures the subtractive color mix using red, yellow and blue (RYB) as primary colors!

How to Use the App?
To use the app you need a white surface such as a white paper. Hold the white paper to the left of the color you would like measure. Direct the camera of your Android(TM) device so that the paper is filling up the left rectangle in the app and the color to be measured is filling up the right circle in the app.
To get correct results you need to make sure that the same light is falling on both the white paper and the color to be measured. Avoid any shadows on the paper of the color measured. This is more important that usually expected. Then press the "Measure" button to let the app measure the color in the circle. The app will then tell how much red, yellow and blue paint or dye you need to mix in order to get that color.

What is Subtractive Color?
This application calculates the subtractive color mix. This is a completely different thing then the additive color mix that most are familiar with today since this is applicable on computer monitors, digital photography and so forth.
You can think of subtractive color mix as a mix starting with a white surface. Then paints, dyes or inks are added to darken and to color the surface with all kind of colors. The more colors added the darker the result. The paints or dyes used are often the three primary colors red, yellow and blue. A mix of these colors can create most colors and hues.
The additive color mix used in computer science is the opposite. To understand additive color mix you can think of something starting with a black surface. From behind this surface start to light up from colored lights. The more light the more bright and white the the result will be. Using the usual setup of red, green and blue lights allows to create all the colors you see in monitors and in digital photography.
This app deals with subtractive color mix using the primary colors red, yellow and blue.

Calibration
In order to help the application measure the colors correctly you can calibrate it against the current lighting conditions. To do that, press the "Calibrate" button, point the camera towards a white surface filling up the screen and press "Calibrate" again. The app will then adjust to the current lightning conditions.

Physical Limitation
It is not possible to mix red, yellow and blue paint or dye to create all possible colors and hues. Most importantly, total black can not be created with any mix of these colors. It is possible to come close if the maximum amount (represented as 1.0 in this app) is used of all the colors together. With this mix you will get dark brown. In all the cases where it is not possible to find an exact mix the app calculates the closest possible mix.

How Accurate are the Measurements?
A number of issues makes it hard to measure the color exactly. The largest errors will appear if the light falling on the paper and on the color you measure are not identical. This can happen if the Android(TM) or the hands of the user is shadowing the light or if the light got reflected on the hands or any other nearby objects that are not white. The effect of these lightning circumstances are much larger than one might expect.
Secondly the Android(TM) devices are slightly different from each other. However, both of these problems are effectively eliminated when the app is used for comparison measurements. In other words, when the app is used in exactly the same lightning conditions on the same Android(TM) device, two measurements on different colors can be compared with typically only small errors in the measurement.

Got Feedback on the App?
Please send any feedback, ideas or improvement suggestions on the application to folkstedt@gmail.com.