problemes with the picture exposition time

I use superlab 4.0 in a window PC for an experiment and we have met problems with the picture exposition time.
We 've got 2 times of exposure : 240 ms , 80ms and we have created a bucle between the picture (For exemple : picture A 240ms, picture B 80ms, picture A 240 ms, picture B 80 ms, etc…) But when we check this time in the result file, it never corresponds. It’s always upper and besides, the first picture exposition is always longer.
while it’s very important for us to have this exact time exposure.

Does a picture library exist in superlab 4.0 in order to verify if with pictures belong to superlab we met the same problem?

Thank you very much for your kind help

This has been discussed in depth on here. Here’s one thread:

It’s only possible to get 80ms if you have certain refresh rates on your monitor, as images can only be displayed in multiples of the refresh rate. If your monitor is running at 60Hz, the closest to 80ms is actually 83.3ms.

SuperLab is capable of providing extra information through its verbose log. This hidden feature was introduced in SuperLab 4.0.3. Directions for how to enable this are included here for Windows and here for Mac OS X. This spits out a very large amount of information in a window after you’ve run your experiment. It’s not pretty, as it’s basically a big list of everything that happened while the experiment was running with time stamps of .01ms precision.