Stimulus size on the subject screen
Posted by Jaewon
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Stimulus size on the subject screen February 17, 2023 01:13PM |
If the size of your subject screen is larger than 20 degrees, you will see some discrepancy between the stimulus size calculated with the pixels per degree (PPD) and the actual size on the screen. It is because the tangent function is not linear beyond the angle of 20 degrees. It is a mathematical principle. There is no obvious solution to this, if you are using a 2-D screen.
If you want to reduce the discrepancy around the center of the screen while using a large screen (but the error outside the 20-degree range will be much larger), turn on the Adjust option next to Pixels per degree on the menu. It fixes PPD to that of one central degree rather than the average across the entire screen.
If you do not see that option, please update your NIMH ML.
If you want to reduce the discrepancy around the center of the screen while using a large screen (but the error outside the 20-degree range will be much larger), turn on the Adjust option next to Pixels per degree on the menu. It fixes PPD to that of one central degree rather than the average across the entire screen.
If you do not see that option, please update your NIMH ML.
