Font size not linear conversion to pixel
hi, I am conducting a visual acuity experiment and I should convert the size of letters (in font Sloan) to px and then have a value in arcmin. The size of the letters is set like that because based on the performance they increase or decrease. I used the above line of code my_canvas['char'].font_size =250 to change the font size. This is the command used and is called every trial with a size that varies from trial to trial. The font used is a SLOAN font (this one: denispelli/Eye-Chart-Fonts (github.com)). I tried measuring the letter when presented and it measures 179px (I set 250 with the last line). For the measurement, I simply made a screenshot at full resolution and then measured with editing programs the size of the letters. Do you know why? Can anyone give me a formula or an explanation for this phenomenon?