The support act is the bands/artists that starts before the main bands/artists It's a band or artist that warms up the crowd before the actual artist comes on stage. Perfect to practise your settings on. The bigger bands like U2, Rolling Stones and Bon Jovi use these bands/artists to open for them, these can vary from local bands/artists to more popular bands/artists.
Are you actually saying that 200 ISO is better as 400 ISO??