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. 2016 Apr 6;4(7):e12746. doi: 10.14814/phy2.12746

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© 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Measuring luminance contrast. (A) In the model, an image is convolved (*) with both an antagonistic and a low‐pass filter. The antagonistic filter output is divided (normalized) by the low‐pass output. Half‐wave rectification is used to segregate bright (ON) and dark (OFF) responses without additional nonlinearities. (B) A disk in equal steps of Weber contrast from 0 to 100%, either decremental/dark (left) incremental/bright (right). (C, D) Predicted ON and OFF contrast response functions for the antagonistic stage alone (C) and the full model (D). (E, F) Response functions are shown as in (C, D), except the stimulus background level was increased by a factor of two. The ordinate scales are matched for C/E and D/F.