I've taken a closer look at my lenses and google has failed to provide the answers, so I'm wondering if you know? You probably do! What's this on my Vivitar Series 1 300m f/5.6 (serial 37XXXXXX): The EE and M with the slidy button underneath? DSCF7660 by Tosh31, on Flickr And this (the silver button depresses): DSCF7661 by Tosh31, on Flickr And can I ask why do they have a left and right aperture scale? It only appears to rotate in a manner that the green scale is used. And is there a relationship to these to the similarly coloured distance scale above them? Also what's the aperture scale for - the one above the aperture ring? And why are two of the markings in red (5.6 and between 16 and 22). Oh, and why are two f.5.6 (one in green and the other in orange)? DSCF7663 by Tosh31, on Flickr And my very last question (apologies), what's this red line for on my Vivitar Series 1, 70-210, f/3.5 (Ser 37XXXXX): DSCF7664 by Tosh31, on Flickr Thanks in advance!