![]() ![]() ![]() It was captured with a Canon EOS-40D camera, 24-70mm f/2.8L lens set at 50mm, f/5.6, ISO 100. The image above used to compare Star chart results with Slanted-edge SFR and Log Frequency. Because calculations are performed on circles of known spatial frequencies, the results are more robust against noise than Log Frequency, which also uses a sinusoidally-modulated pattern. This method is more direct than the slanted-edge method, but requires more real estate. Although sinusoidally-modulated patterns are usually preferred, bar (square wave-modulated) patterns will work with an appropriate normalization setting. Star Chart measures MTF from a star pattern along the radii of a circle for a range of angles (in 8, 16, or 24 segments). Photographing the chart and running the program ISO 12233 recommends 144 or 72 cycles.) Several options are provided for calculating the value of gamma used to linearize the chart and for the low frequency reference. ![]() (24 and 16 cycles are new in Imatest 5.0, but are not recommended for most applications. We’ve made several enhancements in Imatest 5.0.Ĭharts with 144, 72, 48, 36, 24, and 16 cycles can be analyzed in 8, 16, or 24 segments around the circle. But we strongly support the Siemens Star, which provides information on angular MTF response and is the only pattern other than the slanted-edge that can reliably analyze MTF response above the Nyquist frequency. For most purposes we recommend the slanted-edge, which provides accurate reliable measurements, runs fast, and can produce highly detailed maps of sharpness over the image surface. Sinusoidally-modulated stars are preferred, but bar (square wave-modulated) Siemens stars can also be analyzed for MTF, with appropriate normalization settings.Ī detailed comparison of Siemens Star and slanted-edge MTF results is presented in Slanted-edge versus Siemens Star – A comparison of sensitivity to signal processing. Star Chart, which can be run in the interactive Rescharts interface or as a fixed (batch-capable) module, measures SFR (Spatial Frequency Response) also known as MTF (Modulation Transfer Function) from Siemens star charts, which are included the ISO 12233:2014 standard. Introduction – Creating, photographing, running – Output – MTF – MTFnn, MTFnnP ![]()
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