Radial Distortion Self-Calibration

In cameras with radial distortion, straight lines in space are in general mapped to curves in the image. Although epipolar geometry also gets distorted, there is a set of special epipolar lines that remain straight, namely those that go through the distortion center. By finding these straight epipolar lines in camera pairs we can obtain constraints on the distortion center(s) without any calibration object or plumbline assumptions in the scene. Although this holds for all radial distortion models we conceptually prove this idea using the division distortion model and the radial fundamental matrix which allow for a very simple closed form solution of the distortion center from two views (same distortion) or three views (different distortions). The non-iterative nature of our approach makes it immune to local minima and allows finding the distortion center also for cropped images or those where no good prior exists. Besides this, we give comprehensive relations between different undistortion models and discuss advantages and drawbacks.

Selectivity and timing abilities of international socially responsible funds

This article analyses the selectivity and market timing abilities of international Socially Responsible Investment (SRI) funds, from eight European markets, in comparison to conventional funds with similar characteristics. The results show that differences in market timing abilities of international SRI funds and their conventional peers are not statistically significant. However, SRI funds investing in European equities are significantly worse stock pickers than conventional funds, whereas for funds investing globally, selectivity abilities are similar among both fund groups. Hence, our results suggest that a broader investment universe might increase SRI fund managers’ stock picking abilities and, consequently, improve SRI fund performance.