Question: How to adjust units to match actual measurments on screen?
Answer: To adjust the ruler you must use the calibration wizard. Quick step-by-step guide follows:
(1) Click "Preferences" and go to "Displays" tab.
(2) Click "Detect Displays" button, then
(3) select the monitor in the list (all monitors will be added as item 1, 2 etc.) Click to select "1" for the first screen ("2" for the second screen etc.)
(4) In the right side you'll see several fields (widht, height etc.). Set the proper settings in the "Diagonal" field (must be the exact value of the monitor visible diagonal).
(5) Click "Set to Display" button. That should set the units to be as close to the real world as possible for computer screen. If you want to calibrate to given preexisting image, open the image in the ruler and play with the PPI settings until you get the result wanted (you can edit the PPI directly in the grid list of the monitors)
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