[Conversion of .pictClipping picture format]

In order to imput live s-video into my computer with firewire using the formac converter, I must use the application Formac StudioTVR 3. I need to take still images of the video on the screen. In Formac StudioTVR, you do this by dragging the video to the desktop, and it makes a picture clipping of it (whichs sucks, I wish there was a better program to take still pics). Is there a way to make these clipboard images default to jpg format (converting would not be productive, and hard for the less computer literate in my lab). If not, how may I convert these? Futhermore, if any of you out there know of any application that allows for easy still image capture for a firewire converted s-video source, please inform me of it.
Thank you for any help.