Talk:Focus Lens/@comment-24.4.66.97-20180205144340/@comment-74.133.120.217-20181229100426

that is simply wrong... having multiple Eidolin lenses would increase your gain of focus. because it's only 2.5% of the affinity that item gains is converted into focus. Ideally, if you want to grind one school up hard,  only equip 1 weapon with that school of eidolin with a warframe with that school and no pet. that way, all affinity that you earn, and all affinity that you get from allies, will be going towards that school.

Say you had 3 weapons and your warframe with just your melee weapon with an eidolin lens, you'd be getting ((1*0)+(1*0)+(1*0)+(1*0.025))/4 = 0.00625 = 0.625% of all affinity your allies gained as focus. and   ((1*0)+(1*0.0025)) = 0.0125 = 1.25% of all affinity dealt with your melee weapon as focus. any kills with your pistol, rifle, or warframe abilities would provide no focus.

Best bet, if you have just a single lens, is to put it on your favorite/best warframe, because all affinity that you gain, the warframe siphons some of it off to itself.