MetaCow Spectral Image Database
METACOW: A Public-Domain, HighResolution, Fully-Digital, Noise-Free, Metameric, Extended-Dynamic-Range, Spectral Test Target for Imaging System Analysis and Simulation
Standard, easily accessible, test targets have long served the field of color imaging as a foundation for comparison of the performance of various imaging systems and algorithms and the open and meaningful exchange of research results. This website details the creation and application of a new digital color test target useful for research and development of color imaging systems. The target has several advantages over previous types of targets that include spatial resolution, dynamic range, spectral resolution, metameric properties, lack of noise, and continuous tonal variations. All these features can be important for visual assessment, computational analysis, and colorimetric evaluation. This target, known as METACOW, is freely available to all performing research in color imaging.
METACOW is basically a very large (4200 x 6000 pixel) full-spectral image. It is rendered at 5nm increments, between 380 to 760...and is thus about 3gigs in size. It is designed such that both halves of each "cow" appear to match when illuminated with CIE D65, and viewed with the CIE 1931 Standard Observer. This is the example shown above. Each half of the cow is actually maximally metameric with itself. The left half of each cow has the spectral reflectance of the GretagMacbeth Color Checker, while the right half is a Metameric black that has been specially calculated to maximize color difference under Illuminant A. This type of target is designed to test both illumination and spectral responsivities for digital imaging solutions. Examples of illuminant (left) and observer (right) metamerism are shown below.
The image on the left above was rendered under Illuminant A with the CIE 2 degree Observer, and then converted to display sRGB using the CIECAT02 chromatic adaptation transform. The image on the right was rendered under D65 with actual digital camera spectral sensitivities. The metameric nature of the METACOW target should be readily apparent from these examples.
The METACOW test target available for download, for use in imaging system
design and evaluation. We ask only that you credit the Munsell Color Science
Laboratory in any publications. Note that it is a large image; make sure you
are on a decent internet connection for the download. Included in the files
are: many GB of fullsize METACOW Glory, Smaller and Easier to Manage MINIMETACOW,
Matlab Source Code for Reading and Rendering METACOW, and Much More. Or you
can download a smaller version (420x600x77).
Small METACOW Images
Large METACOW Images (500MB file!)