timed capture using an webcam

hi..

i am working with a face recognition project.I have a GUI with an axes and a pushbutton 'START'. Pressing 'START' starts the video onject and displays the preview in the axes.I have to press another button 'CAPTURE' to get a snapshot.

However,i want the functionality that the webcam captures automatically after pressing the 'START' button, while satisfying certain light conditions. I am quite new to timers and cant figure a way out.

Kindly help me....thanks a lot.