D&D 5E (2014) Passively Perceiving in Dim Light

[Asisreo]

We can all agree darkvision isn't a perfect mode of vision since PC's can only see in dim light and therefore have disadvantage in perception checks that rely on sight. My problem is that I don't know if passive Perception relies on sight and takes the -5. I mean, hearing ability hasn't been disabled, so what's the deal?

 

[Flamestrike]

In practice, the dim light penalty is rarely applied, seeing as in order to be 'Hidden' you need to be unseen, and you cant be unseen in dim light (barring Skulkers and similar things that can Hide in light obscurement).

Ditto if they are hidden behind something, you cant see them, so your perception check also doesnt rely on sight.

PCs with the Skulker feat, Wood elves and the like make good use out of the penalty though.

 

[Asisreo]

In practice, the dim light penalty is rarely applied, seeing as in order to be 'Hidden' you need to be unseen, and you cant be unseen in dim light (barring Skulkers and similar things that can Hide in light obscurement).

Ditto if they are hidden behind something, you cant see them, so your perception check also doesnt rely on sight.

PCs with the Skulker feat, Wood elves and the like make good use out of the penalty though.

What if they are unseen in darkness outside of the darkvision's range but eventually get put into the range or walk into the range themselves? Both PC and NPC.

 

[Oofta]

It's going to depend on a lot of factors. Generally speaking I just go with passive perception being a -5. But if it makes sense that the perception is based on sound then it doesn't matter.

 

[Flamestrike]

What if they are unseen in darkness outside of the darkvision's range but eventually get put into the range or walk into the range themselves? Both PC and NPC.

If they're hiding outside of the range of the PCs darkvision (and thus in darkness) its NOT a Perception check 'relying on sight' to notice them, so no disadvantage.

If they step inside the PCs dim light darkvision range, but otherwise have nothing to hide behind, they're automatically seen seeing as they're now only in light obscurement (and only Skulkers and Shadow Demons and the like can Hide in dim light).

If they're hiding behind something AND inside the PCs range of darkvision, it's also not a Perception check that 'relies on sight' (they cant be seen) so again, no disadvantage.

The penalty rarely comes up.

 

[Asisreo]

If they're hiding outside of the range of the PCs darkvision (and thus in darkness) its NOT a Perception check 'relying on sight' to notice them, so no disadvantage.

If they step inside the PCs dim light darkvision range, but otherwise have nothing to hide behind, they're automatically seen seeing as they're now only in light obscurement (and only Skulkers and Shadow Demons and the like can Hide in dim light).

If they're hiding behind something AND inside the PCs range of darkvision, it's also not a Perception check that 'relies on sight' (they cant be seen) so again, no disadvantage.

The penalty rarely comes up.

Can't they just be poorly hidden? Like a tail peeking from a rock?

 

[Flamestrike]

Can't they just be poorly hidden? Like a tail peeking from a rock?

DM's call.

It helps to think about what the PCs will notice with a successful Perception check before they make the check (what it is they're trying to notice). Once you've done that, you can determine if it's a visual check or not.

 

[Harzel]

Can't they just be poorly hidden? Like a tail peeking from a rock?

Ultimately, it's up to the DM, but I think most interpret the "guidance" given in the rules to mean that if you can be seen, then you cannot be hidden. If you can be hidden and you attempt to hide, then the Dexterity(Stealth) roll determines whether you are well hidden or poorly hidden.

 

[Oofta]

Ultimately, it's up to the DM, but I think most interpret the "guidance" given in the rules to mean that if you can be seen, then you cannot be hidden. If you can be hidden and you attempt to hide, then the Dexterity(Stealth) roll determines whether you are well hidden or poorly hidden.

You have to be clearly seen. What that means is up to the DM.

 

[Prakriti]

Keep in mind, disadvantage on Perception is also relevant for the purposes of detecting traps and secret doors and such. PCs are less likely to succeed in these activities in dim light.

When it comes to hiding, it's worth remembering that Dexterity (Stealth) has its roots in two skills from previous editions: Moving Silently and Hiding. You'll see evidence of this in certain monster abilities (Wolves have advantage on checks that rely on hearing, Owls on checks that rely on sight, etc.) and magic items (the Cloak of Elvenkind helps you with hiding, while the Boots of Elvenkind help you with moving silently). There are even some creatures (such as the aforementioned Wolf) that have advantage on checks that rely on smell, in which case, your Boots and Cloak of Elvenkind might not help you at all.

What this all means is that every time someone hides or tries to be stealthy, the DM has to decide which senses come into play and what environmental factors might be impacting them (such as dim light, a smelly garbage pit, or a roaring waterfall). There's no hard-and-fast rule for all of this, unfortunately. It just means judging every case on a case-by-case basis.