Prerelease and data logging

[Paul Groot]

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.westbrook 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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