[visionlist] CRT Vs LCD

[Maximilian Bruchmann]

Dear all,

we recently bought an LCD (LG1970HR) in order to use it in our MEG 
chamber. We know that this is not an optimal presentation device but 
since it appears to be much better than the often used video beamer, 
here are some issues that might concern others in a similar situation:

We put an oscilloscope to the screen and presented white or black 
rectangles on gray background for one frame (as far as I know, people 
define gray-to-gray in different ways, so this is our definition). We 
ran the monitor at 60Hz and at its maximum rate of 75Hz. The latter can 
only be run using VGA, not with DVI.

Every "feature" of the monitor was turned off, i.e. in our case the so 
called fEngine which is supposed to increase display quality for e.g. 
text reading or movies. (You have a big problem, when LCDs have features 
that can not be turned off. E.g. some calculate the mean brightness of 
each screen and add a certain amount if it gets too dark. That may be 
fine for watching movies but not for running experiments!)

The combined rise- and fall time we measured was about 4-5 ms, but I 
have to admit that we did not specify any saturation point but simply 
looked where the plateaus were reached.

I assume it depends on the monitor, but with ours, all backlighting 
effects (reflected by a 260Hz component) disappeared, when the monitor's 
brightness was set to 100%. In that case our oscillations looked just 
like those in the viewsonic document. No filtering necessary.

Open issues are chromatic accuracy and a slightly inhomogeneous light 
distribution across the screen.

Best regards,
Max

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Maximilian Bruchmann, PhD
Institute for Biomagnetism and Biosignalanalysis

Address:    Malmedyweg 15
            48149 Münster
            Germany
Phone:      +49-(0)251-83-56884
E-Mail:     Maximilian.Bruchmann at uni-muenster.de
Internet:   http://biomag.uni-muenster.de
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