elemental penetration

The tooltip is confusing me. Can penetration drop enemy resistance to below zero, effectively meaning increased damage? Or does it stop at zero, so overspeccing is a waste?

I know it could go below zero in POE1. I am currently at 81% with more readily available.

Cant go below 0. However you can use exposure to drop their resistance to negative numbers.

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Syncfx#4604 wrote:

Cant go below 0. However you can use exposure to drop their resistance to negative numbers.

This is so confusing to me. In poe1 I thought pene could go negative but exposure could not? Based on this thread, exposure cant go negative either.

https://www.reddit.com/r/pathofexile/comments/1hbb23t/help_with_understanding_exposure/

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mtlhed667#7816 wrote:

The tooltip is confusing me. Can penetration drop enemy resistance to below zero, effectively meaning increased damage? Or does it stop at zero, so overspeccing is a waste?

I know it could go below zero in POE1. I am currently at 81% with more readily available.

Ive done some good testing on this with info from someone else on the forums.

Basically you can run 30% pen and use your support for the exposure, if thats how you grab it I only know for lightning arc spell. You won't need more than 30% flat pen except the maps that have 50% increased ele res. I think exposure is 20% or 30% and that is with no magnitude.

Basically from what I see even on rares and bosses. They don't take more damage if you get to much, you just end up that you are wasting points in your tree for the penetration. It's worth noting I play Arc so obviously I'm not doing a crit build as then you aren't shocking with it. A crit build may benefit more but you're already getting double damage on every crit minimum.

Isnt pen not a flat value? Ie you reduce enemy res to 30% with exposure/curse, and then if you had 33.333333 (repeating of course) penetration, wouldnt you be hitting then as if they had 20% res?