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slanted-edge algorithms for calculating MTF/SFR are based on ISO 12233 standard, “Photography – Electronic still picture cameras – Resolution measurements”.
Although this standard is well-established in industry, we often receive questions regarding its validity.
Several edges are “binned” and averaged in a sophisticated process described in the ISO standard.
The slant makes the measurement insensitive to sampling phase (edge location relative to pixel locations).
The slanted-edge is compared with other MTF calculation methods here.
The SPIE (the international society for optics and photonics) definition of MTF is in a sine pattern, modulation MTF values are compared with MTF values from SFRMAT3 using the same set of images.
In the second approach, MTF values will be calculated for sine pattern using Image J and Excel.
Although the sine pattern and slanted-edge methods have very different algorithms, they are mathematically equivalent.
A simple one is to run Imatest Test Charts, selecting SFR: quadrants, setting Contrast ratio to maximum and Gamma to 1, and then clicking Create test chart.
A perfect system would have flat frequency response (no rolloff).
A perfect edge would be a step (though anti-aliasing considerations makes this more complex with slanted edges).
These files all start with the same image, but one is an unblurred original and the others are blurred to various degrees by an image editor program.
The blurring is uniform throughout the image (unlike most consumer digital cameras, which have nonuniform processing: sharpening (high frequency boots) near edges; noise reduction (lowpass filtering) in their absence). Both the sine and slanted edges in the test pattern were created digitally.
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Though abstract (not as direct as sine pattern measurements), it has several concrete advantages over sine patterns: it requires less real estate, it is more immune to noise, and it is very robust and repeatable.