two screens, two refresh rates: timing?

[Tobias]

I don't have a switch but a graphic card with two outputs. What I can
do in my graphic card settings is to select the primary screen. And
actually that seems to be the crucial part.

The weaker screen (60 Hz, i.e. refresh circle of 16.6 ms) and the
better screen (100 Hz, refresh circle of 10 ms) are NOT used as
several devices in my E-Prime 2 settings.

I presented two slides (black and white) with a to-be duration of 38
ms each. This should round up to 40 ms for the 100 Hz screen and is
quite far from anything the 60 Hz screen can do (33.3 ms or 50 ms).

If the faster screen is the primary one, I see artificial shapes or
borders on the slower screen but presumably perfect black-white
switches on the faster screen.
If the slower screen is the primary one, it is exactly the other way
round.

More interestingly, I logged the duration errors and onset delays.
Duration error was always 0 which seems to be due to the way E-Prime
records the timing, see an earlier post my David. The onset delay,
however, was -5 ms if the slower screen was the primary one. This
somehow makes sense as two circles are 33.3 ms. As the screen was
supposed to show the stimuli for 38 ms, it is an "delay" of -5 ms. If
the faster screen was the primary one, the delay was always 2 ms which
also makes sense, it just can't stop after 38 ms because a full
refresh circle is 40 ms, i.e. 2 ms more.

Alltogether, I assume that the refresh rate of the primary screen (as
set in Windows) defines for how long a stimulus is actually presented.
The secondary screen will show flickering if it's refresh rate does
not fit the to-be duration of the stimulus.

I hope this is helpful for others who use two screens.

Best,
Tobias

P.S.: The 100 Hz flatscreen we use here is the Samsung Syncmaster
2233BW.


On 14 Jul., 15:36, Michiel Spape <Michiel.Sp... at nottingham.ac.uk>
wrote:
> Hi,
> You're shooting topics around, aren't you :) Anyway, this is just to say: my experience is terrible, dreadful and horrible, when using screens in certain modes. Perhaps it is because we're using a switch, but essentially, I can do whatever I like, the screen in my lab won't do anything other than 60 Hz (on a CRT screen, mind you). A number of times, I got it to work better, but fidgeting with the small settings in the video driver menu is a nightmare. If you use E-Prime 2, you might be able to use multiple monitors in a more sane way, 'send this to display1, this to display2', and that ought to work. I imagine, however, that in my own situation (E-Prime 1), there is no such thing as 2 refresh rates; the primary system is the only thing that "exists", as far as E-Prime is concerned.
> Anyway, very few tips from my side, just a word of caution: whether your E-Prime will say refresh rate is brilliant or not, see it for your own eyes anyway. On a CRT screen in a dark room, using the corners of your eyes, you should be able to see the difference between 60 Hz and 100 Hz.
> Best,
> Mich
>
> Michiel Spapé
> Research Fellow
> Perception & Action group
> University of Nottingham
> School of Psychologywww.cognitology.eu
>
> -----Original Message-----
> From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf Of Tobias
> Sent: 14 July 2011 13:42
> To: E-Prime
> Subject: two screens, two refresh rates: timing?
>
> Hi,
>
> in our lab we have a brand new flat screen that can run at up to 120
> Hz (I use it at 100 Hz right now). We also have an additional screen
> in the neighbor room to check if everything is alright with the
> stimuli presented, to see the feedback the subjects gets etc. Anyway,
> this second screen is not able to run at such high refresh rates. I
> have set the screens as "clone".
>
> I am wondering how E-Prime handles this concerning duration error,
> onset delay, screen sync etc. Any experience with that?
>
> Best,
> Tobias
>
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