Ganito ba sayo?
LIGHT-->glass-->>tracing paper-->>screen-->>foam. A 1/4 thick glass is good enough as a counter-weight against the bottom foam to have a zero gap (good contact) between your tracing paper against the screen.
LIGHT-->glass-->>tracing paper-->>screen-->>foam. A 1/4 thick glass is good enough as a counter-weight against the bottom foam to have a zero gap (good contact) between your tracing paper against the screen.