Image Analysis Tools

Multispectral Image Calibration and Analysis Toolbox

Digital cameras can be powerful tools for measuring colours and patterns in a huge range of disciplines. However, in normal ‘uncalibrated’ digital photographs the pixel values do not scale linearly with the amount of light measured by the sensor. This means that pixel values cannot be reliably compared between different photos or even regions within the same photo unless the images are calibrated to be linear and have any lighting changes controlled for.

Some scientists are aware of these issues, but lack convenient, user-friendly software to work with calibrated images, while many others continue to measure uncalibrated images. We have developed a toolbox that can calibrate images using many common consumer digital cameras, and for some cameras the images can be converted to “animal vision”, to measure how the scene might look to non-humans. Many animals can see down into the ultraviolet (UV) spectrum, such as most insects, birds, reptiles, amphibians, some fish and some mammals, so it is important to measure UV when working with these animals. Our toolbox can combine photographs taken through multiple colour filters, for example allowing you to combine normal photographs with UV photographs and convert to animal vision across their whole range of sensitivities.

Paper: Troscianko, J. & Stevens, M. 2015. Image calibration and analysis toolbox – a free software suite for objectively measuring reflectance, colour and pattern. Methods in Ecology and Evolution. 6: 1320–1331.