When they used the twinkle-wall it's especially obvious because the "stars" look a bit larger and their "aura" sort-of overlaps the other lights and stuff. (I don't know what this effect is called.)
It's noticeable here:
		
		
	
	
		
	
Compare that close-up shot with the view-screen in it to the Troi one above, apparently, using the green/blue-screen.
Most noticeably how the "close up" of the lights in the wall shows the inherent flaws in the process.
	
		
			
		
		
	
				
			It's noticeable here:
	Compare that close-up shot with the view-screen in it to the Troi one above, apparently, using the green/blue-screen.
Most noticeably how the "close up" of the lights in the wall shows the inherent flaws in the process.
				

	