I am new canon eos 40d user,I usually get green flashing light in side view finder but i cant get it now ,why?

Question

I got these green light when i half press the shutter button,But i get only red now when i press the half shutter button,Any idea?

Answer 1

That light is the focus confirmation. If it's red it means it can't focus on whatever you're pointing it at.

Answer 2

the manual will tell you why

Answer 3

As "hipp5" said, it is the focus confirmation light.

Try focusing on something a bit further away. If it still doesn't work, check that the little switch on your lens is actually set to auto focus.

That light doesn't come on when it is set to manual focus.