# visual angle

**URL:** <https://psychtoolbox.discourse.group/t/visual-angle/253>\
**Category:** Uncategorized\
**Created:** [June 19, 2014, 12:57pm UTC](https://psychtoolbox.discourse.group/t/visual-angle/253 "2014-06-19T12:57:11Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\
**Post date:** [June 19, 2014, 12:57pm UTC](https://psychtoolbox.discourse.group/t/visual-angle/253/1 "2014-06-19T12:57:11Z")

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Dear all,

 My question might sound quite naive, but, I present the stimuli in the center of a 21 inch LCD monitor which is 90 cm away from the subject. How can I explicitly describe the stimulus location in terms of vertical and horizontal degrees, what is the algorithm or calculation for that?

 

best,

Sibel

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**Author:** ![dcnieho](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@dcnieho](https://psychtoolbox.discourse.group/u/dcnieho)\
**Post date:** [June 19, 2014, 6:45pm UTC](https://psychtoolbox.discourse.group/t/visual-angle/253/2 "2014-06-19T18:45:42Z")

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For your setup, this will work fine. Do note that angular distance does not scale linearly with distance on the screen once you get out to above about 40 degree, then things get more complicated in that you have to calculate each directly by adapting Alan's formulae

  
  

> On Thu, Jun 19, 2014 at 4:40 PM, Alan Robinson [arcogsci@...](mailto:arcogsci@...) [PSYCHTOOLBOX] \<[PSYCHTOOLBOX@yahoogroups.com](mailto:PSYCHTOOLBOX@yahoogroups.com)\> wrote:  
> 
> > as matlab code:  
> > 
> >   
> > %width and dist measurements fall out so just be sure to use the same  
> > %units for both (currently, inches)  
> > hRes = 1920; hSize = 41; vDist = 57; % LG TV 46 pix per deg  
> >   
> > degPerPix = 2\*atand( (hSize/hRes) / (2\*vDist))  
> > pixPerDeg = 1/degPerPix  
> > 
> >   
> >   
> > 
> > On Thu, Jun 19, 2014 at 5:57 AM, Sibel Ozer [sibelozer.ege@...](mailto:sibelozer.ege@...) [PSYCHTOOLBOX] \<[PSYCHTOOLBOX@yahoogroups.com](mailto:PSYCHTOOLBOX@yahoogroups.com)\> wrote:  
> > 
> > > Dear all,
> > > 
> > > My question might sound quite naive, but, I present the stimuli in the center of a 21 inch LCD monitor which is 90 cm away from the subject. How can I explicitly describe the stimulus location in terms of vertical and horizontal degrees, what is the algorithm or calculation for that?
> > > 
> > >  
> > > 
> > > best,
> > > 
> > > Sibel