Measurements based on slanted-edges accurately represent real-world performance: they work extremely well for testing of cameras in wide range of applications, from product development to manufacturing. Low contrast (4:1) slanted-edges closely approximate features our eyes use to perceive sharpness, and they rarely saturate the image.

The relatively high contrast of the Siemens Star (specified as >50:1) makes measurement results quite sensitive to clipping and nonlinearities in tonal response. To summarize our results, we found that sinusoidal patterns are sensitive to sharpening, though often less so than low contrast (4:1) slanted-edges. The Siemens Star is of particular interest because, along with the slanted-edge, it is included in the ISO 12233:2014 standard.

In this page we address concerns about the sensitivity of slanted-edge patterns to signal processing, especially sharpening, and we correct the misconception that sinusoidal patterns, such as the Siemens star, are insensitive to sharpening, and hence provide more robust and stable MTF measurements. A comparison of sensitivity to signal processing

Siemens star focus chart