When I watch an individual frame my display is good in the composition panel.
But when i Play using spacebar of Preview panel the quality of the view is bad. I can't even read my big titles anymore.
I have this problem on 2 laptops of students.
I think it is GPU-related, but I don't know how to fix it.
when you playback your scene, you should look into your playback settings in the preview panel. if you are using space bar then see what settings are applied to the space bar preview:
check under resolution. when it's set to Auto, it will preview in the resolution you set in the composition panel. this is probably what most users use. if the preview panel space bar resolution will be set to quarter, and the composition will be set to full - you will preview at quarter but when you stop you will see in full. I am guessing this is what happens in your case.