i just bought a rolleicord today and i realise there is this lever with a red dot on the left side of the TLR, could someone tell me what is that? i'm a total amateur. do i really need a light meter reader to get the right exposure? or can i use a digicam to do my light reading? oh and what does ASA and DIN means? the numbers are too confusing. i haven't touched a film camera before.please help me? if have a chance treat you to coffee.