Hi Mario
i have checked the trintitron, and unfotunatelly , the lines are still there.
regarding the stripes that are visible on the screen, i have tested a sony trinitron multiscan
420GS. The vertical stripes are still there, in addition there are also horizontal ones (that
may have been there in the others as well, just missed since out of focus). I used a
random noise stimulus interrupted with a kbwait to check the size of these things, and i
can tell you that
at 640 x 480 pixel screen setting, with 85Hz refresh rate, each pixel is cut through by one
vertical line, yielding 2 rectangles.
at 1600 x 1200 pixel screen setting, with 60Hz refresh rate, each pixel is within the limits
of one line, so i guess one can use this screen setting. Now your visual stimulus is
actually looking like a backgammon board, with each pixel framed by lines.
An imperfect way is to alter the distance of the objective that collects the stimulus such
that the grid is out of focus, but the pixels are still fairly sharp.
If you make scaled "pixels", so squares of 4x4 pixels, you can also observe horizontal
lines, that occur with a frequency of half the vertical ones.
Pehaps another way is to set the screen way back and create artificially larger pixels. At
that point you can probably get ridd of the lines by moving the focus a little.
I am still kind of puzzled as to why other people have not seen this before.
Tudor
> >
> > In any case, i do have a few old trinitron tubes lying
> > around the lab - nobody wants them, everyone is into
> > flatscreens. So i will have to haul them downstairs,
> > put them in front of my setup and see what happens.
> >
> > That's almost all, until i start data analysis.
> > Cheers, and thanks a bunch.
> >
> > Tudor
> > --- Mario Kleiner <mario.kleiner@...>
> > wrote:
> >
> > > Not an expert, but could it be this what you're
> > > seeing?
> > >
> > >
> > <http://www.epinions.com/cmd-review-68E6-1273DC21-3839F1FF-bd4>
> > >
> > > At high magnification levels you will see the
> > > separating wire arrangemnt,
> > > or mask pattern on a non-Trinitron monitor, or the
> > > transistor matrix of
> > > a lcd panel. Maybe you'll need some kind of diffusor
> > > in front of your screen
> > > to blur the image out?
> > >
> > > "I know everything because i can google, use
> > > Wikipedia and
> > > make things up if i don't know the real answer,
> > > rather than
> > > confess i don't know the answer."
> > > -mario
> > >
> > >
> > > --- In psychtoolbox@yahoogroups.com, tudor badea
> > > <tudorcb@> wrote:
> > > >
> > > > Hi Mario,
> > > >
> > > > here is Tudor, the guy with the ugly bullseye
> > > code.
> > > > That was destined to produce concentric circles to
> > > be
> > > > shown rom quicktime, so it is done with. But i am
> > > on
> > > > to my next project. I will be for the most part,
> > > > presenting visual stimuli to a retina through a
> > > > microscope objective. I am currently setting up
> > > the
> > > > system. So i am looking at this Dell computer
> > > screen
> > > > (with a 85Hz refresh rate), and whenever i use one
> > > of
> > > > the simple things like draw dot or similar stuff,
> > > i
> > > > see some black and white vertical lines running
> > > > through my entire field, underlying whatever
> > > stimulus
> > > > i am presenting. I tried this also by presenting
> > > the
> > > > stimuli from the screen of my PowerBook G4, and i
> > > get
> > > > a simmilar thing. i am wondering whether it is
> > > > because i am missing something fundamental, or
> > > whetehr
> > > > this is what aeveyone sees when they look at a
> > > > computer screen with a magnifying lens (which is
> > > > basically what i am doing here).
> > > >
> > > >
> > > > Tudor
> > > >
> > > >
> > > > --- Mario Kleiner <mario.kleiner@>
> > > > wrote:
> > > >
> > > > > This one...
> > > > >
> > > > > <http://www.rcbi.rochester.edu/~ks/ptb.htm>
> > > > >
> > > > > is a different tutorial by Keith Schneider from
> > > > > Rochester. Up to now
> > > > > the best one i've found related to Matlab +
> > > > > Psychtoolbox-3.
> > > > > The tutorial mentioned by Maria is nicely made,
> > > but
> > > > > refers to
> > > > > the old PTB-2, so many of the practices
> > > demonstrated
> > > > > there
> > > > > don't really apply to PTB-3 any more.
> > > > >
> > > > > Other than that, looking at our PsychDemos is
> > > always
> > > > > a good idea
> > > > > to get ideas on how to solve some tasks and how
> > > to
> > > > > do stuff in
> > > > > an efficient way. You'll have to look at many of
> > > > > them, given
> > > > > that each of them demonstrates different
> > > concepts
> > > > >
> > > > > -mario
> > > > >
> > > > > --- In psychtoolbox@yahoogroups.com, "gilisabo"
> > > > > <gilisabo@> wrote:
> > > > > >
> > > > > > Hi Maria
> > > > > > 10x for your advises, can you send me the link
> > > > > again (this one isn't
> > > > > > working)? any ways, I solve some of my major
> > > > > problems (I find it easy
> > > > > > to program -using good guiding)-but I still
> > > have
> > > > > some questions left'
> > > > > > like: how can I define the spatial frequency
> > > of
> > > > > any given Gabor?
> > > > > > Best
> > > > > > Gilad
> > > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
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> > >
> > >
> >
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>