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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Dear Arun,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Looking at your demo, if I understand it correctly, you express the intensity changes in bit-space, rather than physical luminance space. Is that the case? My assumption would then be
that, as for most monitors, your monitor’s bit-luminance relationship follows a positively accelerated gamma-curve. Would that not explain it?
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">(e.g. <a href="https://www.benq.eu/en-eu/knowledge-center/knowledge/gamma-monitor.html">
https://www.benq.eu/en-eu/knowledge-center/knowledge/gamma-monitor.html</a>).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Sincerely,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Chris Olivers,
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Amsterdam<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> visionlist <visionlist-bounces@visionscience.com>
<b>On Behalf Of </b>SP Arun<br>
<b>Sent:</b> 24 August 2022 18:59<br>
<b>To:</b> visionlist@visionscience.com<br>
<b>Cc:</b> Thomas Cherian <thomasc@iisc.ac.in><br>
<b>Subject:</b> [visionlist] brightness change detection puzzle<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span class="xelementtoproof"><span style="font-family:"Arial",sans-serif;color:black;background:white">Dear visionlist, </span></span><span style="font-family:"Arial",sans-serif;color:black">
<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">We have a brightness perception puzzle in the image linked below. <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="xxelementtoproof"><span style="font-family:"Arial",sans-serif;color:black"><a href="https://drive.google.com/file/d/1QpWT48uA9R1ZG48ERy4F3osvxPgoy4qT/view?usp=sharing">https://drive.google.com/file/d/1QpWT48uA9R1ZG48ERy4F3osvxPgoy4qT/view?usp=sharing</a></span></span><span style="font-family:"Arial",sans-serif;color:black">
<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">When we tried to find the smallest change in brightness detectable against a uniform background, we found something strange: for dark backgrounds, we found
that only large brightness changes could be detected, whereas for brighter backgrounds, we found that much smaller brightness changes could be detected. <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">This was puzzling to us because this is the opposite of Weber's law -- by Weber's law we would expect that the threshold brightness change for brighter backgrounds
should be larger than for darker backgrounds. But we observe the opposite. <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">All this must be because of contrast detection somehow. But we are unable to think of reasons why this is happening. Any ideas? <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">Regards, <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">Arun<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">---<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">SP Arun<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">Professor <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">Centre for Neuroscience<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">Indian Institute of Science<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">Bangalore 560012<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">T: +91 80 22933436 <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:black">W: <a href="https://sites.google.com/site/visionlabiisc" title="https://sites.google.com/site/visionlabiisc">https://sites.google.com/site/visionlabiisc</a><o:p></o:p></span></p>
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