The details of this processing are more complex, or course, and vary greatly for different cameras. Most consumer cameras sharpen images in the presence of contrasty features (like edges) and reduce noise (lowpass filtering the opposite of sharpening) in their absence. Measurements based on slanted-edges accurately represent real-world performance and are well suited for testing of cameras in wide range of applications, from product development to manufacturing.įull details of the comparison are in the Slanted-Edge versus Siemens Star and the Slanted-Edge versus Siemens Star, Part 2 pages, where we compare MTF calculation results from slanted-edge patterns, which are performed by Imatest SFR, SFRplus, and eSFR ISO, to results from sinusoidal patterns, which are performed by the Imatest Star chart (for the Siemens star) and Log F-Contrast modules, paying special attention to the effects of signal processing, especially sharpening and noise reduction (which are performed by software or in-camera firmware). Low contrast slanted-edges (4:1 in the ISO standard) closely approximate features our eyes use to perceive sharpness, and they rarely saturate images. The relatively high contrast of the Siemens Star (specified as >50:1 in the ISO standard) makes measurement results somewhat sensitive to clipping and nonlinearities in tonal response. To summarize our results, we found that the Siemens Star (and other sinusoidal patterns) are nearly as sensitive as slanted-edges to sharpening, and that slanted-edges give reliable MTF measurements that correspond to the human eye’s perception of sharpness. This post addresses concerns about the sensitivity of slanted-edge patterns to signal processing, especially sharpening, and corrects the misconception that sinusoidal patterns, such as the Siemens star (included in the ISO 12233:2014 standard), are insensitive to sharpening, and hence provide more robust and stable MTF measurements.

Siemens star pattern use with ccd