Hi everyone,
I’m trying to measure contrast sensitivity in psychopy using orientation discrimination. I have a problem when people go very low in their sensitivity (<3%). The values I put in no longer seem to be correct after I test them using a luminance meter. Did anyone ever face this issue? What to do? Is it the monitor? Is it Psychopy?
|Contrast_psychopy|W|G|Michelson|
|1|86.4|0.34|0.99216048|
|0.8|83.8|9.35|0.799248524|
|0.64|77.3|17.3|0.634249471|
|0.512|71.5|22.6|0.519659936|
|0.41|66.1|27.3|0.415417559|
|0.328|61.7|31.6|0.32261522|
|0.262|56.2|32.9|0.261503928|
|0.21|53.2|35.2|0.20361991|
|0.168|50.9|38.2|0.142536476|
|0.134|52.4|40|0.134199134|
|0.107|50.5|40.3|0.112334802|
|0.086|47.5|40.6|0.078320091|
|0.069|48.6|42.5|0.066959385|
|0.055|48.1|43.8|0.046789989|
|0.044|47.3|43.5|0.04185022|
|0.035|45|43|0.022727273|
|0.028|45.6|43.4|0.024719101|
|0.023|42.9|42.7|0.002336449|
|0.018|45|43.4|0.018099548|
|0.002|43.5|43.3|0.002304147|
|0.0001|42.9|42.9|0|
As you can see in my measurement table above, for high contrasts it’s all fine, for the lower ones, especially below 4%, things start to get strange. Also, the values change a bit when I do second or third measurements (could this be a sensitivity issue with measurement equipments?)
Any help is (highly) appreciated!