I just bought a used Nikon Speedlight SB-50DX and it seems to work fine, i am just lost when it comes to alot of the settings. what is the difference between Manual and Ttl? What is the zoom button on a flash used for? The flash didnt come with a manual, and i've looked everywhere for online manuals, and nothing has come up. Please give me any tips, or info you might have that would help me know my new flash better!. thanks in advance.