Phosphor Decay Times of Iiyama HM204DT monitors


In order to perform psychological visual experiments in which stimuli have to be presented for very short times, many scientists use CRT (cathode ray tube) monitors. Such monitors produce their picture by means of cathode rays that illuminate phosphor of single points on the screen. Immediately after the activation of the phosphor it starts decaying, i. e. the picture is fading.

If one wants to know how long a picture is presented after its activation one has to measure the time course of this phosphor decay. This was done here by a photodiode and an oscilloscope for the monitor Iiyama HM204DT.


The monitor was run with a resolution of 800x600 and a frame rate of 200 Hz. The contrast was set to 100%. Three levels of brightness have been taken into account: 0%, 50%, and 100%.

For each brightness, the colors red, green, blue, and white were measured, and for each color three different pictures: One single horizontal line on a black background, 10 successional horizontal lines on a black background, and finally the whole screen. Most measurements have been repeated for five times, a few were performed only once.


Each measurement is stored in one single file. The files are archived and can be downloaded here:

The filenames share the following pattern:

BrightnessColorNumberOfLines_Trial.txt, or more precisely:
Br[0 | 50 | 100][Red | Green | Blue | White][[1 | 10]Line[s] | Fullscreen]_[1 | 2 | 3 | 4 | 5].txt

The data is the unprocessed output of the oscilloscope.

Analysis and discussion of the results: I compiled some data analysis and discuss the results in the file


If you have any comments or better ideas than uttered there, do not hesitate to contact me (tobias-elze [ät] tobias-elze [dot] de)

Have fun,


Tobias Elze, 2005.