Talk:Focus Lens/@comment-87.165.96.249-20151222155332/@comment-3391671-20151224032346

If you put the lens on your warframe, you will receive closer to 2.5% conversion if most of your kills are through your weapons. If you kill with your warframe (let's say through an Ash), then the conversion is 5%. These number increase by about 20% if using a greater lens. It's good to note that it's best to kill more with the weapon/warframe with the greater lens if you've equiped one.

As for how many weapons to take, it may be best to take all weapons with a lens (conversion is not hampered by additional weapons with focus lens). If no weapon has a lens, only take one and try to kill with the WF as often as possible. If you only have one WF and one weapon with a lens, to maximize focus conversion, only bring that one weapon with the warframe. Once again, kill with either warframe power or weapon that has the greater lens.