Prerelease and data logging

[Cecilia Westbrook]

Ah, I think I figured it out. Looks like the offsettime is actually 100ms 
early due to prerelease of the next stimulus.

On Thursday, June 5, 2014 1:21:10 PM UTC-5, Cecilia Westbrook wrote:
>
> Hi Paul,
>
> Thanks, this makes sense now that you point it out to me.
>
> I still can't figure out, then, why the onsettime would be 100ms later 
> than the offsettime for the previous stimulus, if the stimulus is 
> prereleased and therefore preparing in the background. There are not 100ms 
> of blank screen when I do the task.
>
> On Thursday, June 5, 2014 5:00:30 AM UTC-5, Paul Groot wrote:
>>
>>
>> from http://www.pstnet.com/support/kb.asp?TopicID=3025
>>
>> *Lastly, it is also important to keep in mind exactly what the Onset Time 
>> property is telling you. The Onset Time property will give you a timestamp 
>> of the exact time in which the display began to draw.*
>>
>> But you will find more relevant pages when you use keywords as eprime, 
>> onssettime, LCD, etc.
>>
>> So, the OnsetTime has no direct relation with the time that E-Prime is 
>> *preparing* the stimulus in memory during the pre-release time of the 
>> previous object. 
>>
>> Note that the actual pixel responses depend on the hardware that is being 
>> used, and the pixel location on the display. If it is really critical, you 
>> should check the real onsets using a light sensor and oscilloscope.
>>
>> Paul
>>
>>
>>
>> On 5 June 2014 00:16, Cecilia Westbrook <ceci.we... at gmail.com> wrote:
>>
>>> Thanks, this is helpful.
>>>
>>> One question that I still can't seem to find the answer for, though, is: 
>>> what does E-Prime log as OnsetTime for an object set with pre-release? Does 
>>> it log when the object starts drawing, or when it actually displays?
>>>
>>> On Wednesday, June 4, 2014 2:47:11 PM UTC-5, Paul Groot wrote:
>>>>
>>>> Hi Cecilia,
>>>>
>>>> You may find one of David's post very informative:
>>>>
>>>> https://groups.google.com/d/msg/e-prime/OeiZ00V9SRc/Vt2QAt3uoOcJ
>>>>
>>>>
>>>> Also note that the prerelease time of an object is used to prepare the *following 
>>>> *object. (This is something that is often overlooked.) 
>>>>
>>>> Paul
>>>>
>>>>
>>>> On 4 June 2014 20:49, Cecilia Westbrook <ceci.we... at gmail.com> wrote:
>>>>
>>>>> Hi all,
>>>>>
>>>>> I'm sure this is covered in another thread, but I was not able to find 
>>>>> it with searches. I'm using E-Prime for an fMRI task with critical timing. 
>>>>> I'm using prerelease for my stimuli, but I'm seeing some weirdness in my 
>>>>> data logging files. For stims with 200ms prerelease, it seems like it is 
>>>>> logging them as the onsettime + 200ms. Shouldn't it be -200ms?
>>>>>
>>>>> I see this in two ways: 1) if I look at the onsettime and the offset 
>>>>> time and subtract them to get a duration, it is 200ms SHORTER than it 
>>>>> should be (seems like it should be 200ms LONGER). 2) If I log the 
>>>>> offsettime of the stim immediately preceeding it, the onsettime is 200ms 
>>>>> later (even though it should be displaying at the same time as the offset 
>>>>> time of the previous stim, right? +/- a little bit of delay in offsettime - 
>>>>> but not 200ms of delay, surely?).
>>>>>
>>>>> What is going on? Does anybody have any advice? Is the most accurate 
>>>>> thing to do to just use the offsettime of the preceeding stim?
>>>>>
>>>>> Thanks,
>>>>> Ceci
>>>>>
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>>
>>

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