Sidepanel on the left

Screen specification

Screen resolution

Enter your horizontal and vertical screen resolution in pixels. The default is 1680 x 1050 pixels.

Screen size

Enter the size of your screen by providing the diagonal in inch or the width in cm or the height in cm. Only one of these is necessary as the remaining ones can be calculated based on the screen resolution. The default is 24 inch.

Viewing distance

Enter the distance between the eyes of the participant and the screen in cm. The default is 70 cm.

Calculator tab

What should the app calculate?

There are two options:

• Stimulus coordinates: Enter visual angles and the app calculates stimulus coordinates in height, norm, pixel and cm units.
• Visual angles: Enter stimulus coordinates using height, norm, pixel or cm units and the app calculates the visual angles.

Stimulus coordinates

The radio buttons under “Choose a unit” allow you to choose a unit for entering your stimulus coordinates. The options are:

• Height
• Norm
• Pixel
• cm

You can find out more about these units on this page about spatial units in PsychoPy. (The Builder demo “spatialUnits” is also very useful to better understand spatial units in PsychoPy.)

If the app is told to calculate visual angles, the numerical entry field corresponding to the chosen type of unit will be enabled; the others fields will be disabled. After entering coordinates, the visual angles will be updated accordingly.

Visual angles

If the option “Stimulus coordinates” is selected, you can enter visual angles in degrees. The stimulus coordinates will then be calculated accordingly.

The plot

The grey rectangle represents your screen. By default, a point in the centre of the screen is shown. In PsychoPy, the centre of the screen always has the coordinates [0, 0], independent of the unit chosen. Once you enter stimulus coordinates or visual angles, the point will move to the corresponding location on the screen. If the point is not on the grey rectangle, you have chosen coordinates that lie outside your screen.

The visualisation of the screen has two sets of axes. The axes on the top and on the right always display degrees of visual angle. The axes on the left and the bottom display axes that correspond to the unit chosen under “Stimulus coordinates”.