Sikuli - Screenshot of a picture on one screen and compare / search on another page

I am creating a script using Sikuli and bump into a wall. I am basically trying to grab a screenshot of a screen and compare / find it on another screen. I have used to capture()

no avail.

Help would be much appreciated.
Here is my simple code. For some reason, it always prints yes.

x=capture(Region(268,856,312,20))  
click("next tab")  
if exists(x):    
    print "yes"  
else:  
    print "no"