User`s guide

E-Prime User’s Guide
Chapter 3: Critical Timing
Page 80
Figure 3. Video display refresh cycle for a 1024x768 display with a refresh rate of 71.4Hz (14ms refresh
duration). The top line of the display is line 0, and the bottom line is 767. Each pixel is displayed once every
14ms.
To calculate the refresh duration in milliseconds given the refresh rate specified in Hz, use the
following equation:
Refresh Duration (ms) = 1000 / Refresh Rate (Hz)
Refresh Duration = 1000 / 71.4
Refresh Duration = 14.0ms
To calculate the refresh rate in Hz given the refresh duration specified in milliseconds, use the
following equation:
Refresh Rate (Hz) = 1000 / Refresh Duration (ms)
Refresh Duration = 1000 / 14.0
Refresh Duration = 71.4Hz
On a CRT monitor, during the refresh cycle the video display hardware activates each pixel for a
short period of time (about 3ms per refresh cycle). Figure 4 shows the typical activation the eye
sees for a pixel in the middle of the display. The example presents a fixation, probe, mask
sequence of “+”, “CAT”, and “***” respectively. Each write of the data to the video hardware is
assumed to occur during a vertical blanking interval (e.g., screen writes performed at offsets of 0,
14, and 28ms). The pixels for the middle of the display (line 384) would be refreshed and
displayed at the approximate offsets of 7, 21, and 35ms.