Talk:Focus/@comment-178.24.154.106-20180411090224/@comment-50.65.102.139-20180413031248

If you get the kill, half of the affinity goes to your warframe, the other half goes to whatever killed the enemy (usually one of your weapons, but sometimes your warframe again). In this case, you only need a lens on the weapon that got the kill, and one on your warframe, and you'll get all the affinity.

If someone else gets the kill, 1/4 goes to your warframe, and the other 3/4 is split between all equipped weapons. If you only have one weapon, then it gets all that affinity and you only need a lens on it (plus the warframe of course) to get it all. If you have more weapons, you will need a lens on each of them, or some of the affinity will go to waste.