This paper demonstrates the relationship between detection errors and resolutions (ρ- and θ- directions) when the Hough Transform (HT) is employed to detect straight segments in images. The inflexion of the error-resolution curve was uncovered. To comprehensively study the location of the inflexion, the effects of several factors are considered, such as the positions (ρ and θ), widths and lengths of straight segments, noise level, and the ratio of resolutions. An error surface according to ρ- and θ- resolutions is obtained in the paper to guide seeking of the best resolutions. The area containing “good” resolution settings is uncovered and modelled.