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Fixed font size in online experiment

Hello, everyone! I am doing an online self-paced reading experiment and hope the text stimuli will be in a fixed size(16 pt). Now the size unit I use is the pixel, and I met a few problems:

  1. I tend to set the text stimulus as 16pt, so I convert it into the corresponding size in pixel, that is 24 pixel. However, the word seems to be smaller than that in 16pt.

  2. Also, I am uncertain whether the font size will change when the experiment is run on different computers.

I am quite new to PsychoPy and use the builder as well as several code components in the current experiment. I appreciate any advice from you! Thank you!

Hi Iris,

Welcome! Having text (or any stimulus) be constant across computers is quite a nuanced undertaking, so I’ll list some topics in bullets below.

  • Computers screens can have different resolutions and sizes, so a pixel can have a different size on each computer. A workaround for this is @wakecarter’s calibration experiment. https://gitlab.pavlovia.org/Wake/screenscale
  • Participants can sit at different distances from their screens, so even if the stimulus size is constant, their size in terms of visual angle can vary. I’m not aware of any straightforward solution for this yet, though W3C’s CSS pixels could offer a solution. We’re hoping to test in the future how stable that is.
  • Moving on to text. PsychoJS uses fonts provided by the operating system, but how those fonts look can vary between computers; they can be be slightly different in size and style between computers. We’re planning on implementing web-font to have more control over this, but this is in an early stage. Here is a prototype.

Best, Thomas

Thank you very much for sharing the links! They are helpful!

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