The easiest way to do this is the following.
Run the film.
When the image of choice appears, rather smartly click on Alt and PrtScr[next to F12]together.
Now stop the film and run up your image editor.
Go to File/New
When the nice new blank page appears, right click tne mouse in the page and select paste.
You will then get an image of the Screen at the instant you clicked Alt/prtScr.
If you were lucky and got the image you wanted
all you need no do now is normal image editing of cropping away surplus and improving image,