Collagen fiber bundles are important constituent parts of biological soft tissues, such as tendons, blood vessels and skin.The single collagen fibers within a bundle have a certain crimp that determines the bundle’s stretching characteristic, which is of particular interest in mechanobiology. A thorough understanding of the complex interrelations between mechanical factors and the associated biological responses may help to improve diagnostics, which allow disease and injury to be treated earlier. We present a method to obtain the relative stretching characteristics (RSC) of collagen (fibrous) bundles based on the analysis of microscopic tissue images. We show, how the orientation statistics of local orientations in a bundle can be directly related to the RSC. The von Mises distribution (VMD) – a circular probability distribution – is used to describe the 2D orientation statistics. The κ parameter of the VMD is used to obtain the mean stretching and the probability density function (PDF) of the bundles’ RSC is identified.