There are a few places throughout the officially published adventures where the Perception DC to spot something differs depending on whether it is an active or passive check. However, this doesn't seem to be consistent. For instance (spoilers for Lost Mine of Phandelver):
The two starting traps on the Goblin Trail have the same active and passive DC:
"If the characters are searching for traps, the character in the lead spots the trap automatically if his or her passive Wisdom (Perception) score is 12 or higher. Otherwise, the character must succeed on a DC 12 Wisdom (Perception) check to notice the trap." (Phandelver, pg.7, my emphasis)
"The character in the lead spots the hidden pit automatically if his or her passive Wisdom (Perception) score is 15 or higher. Otherwise the character must succeed on a DC 15 Wisdom (Perception) to spot the hidden pit." (Phandelver, pg.7, my emphasis)
Whereas in these cases, passive Perception is given a significantly higher DC:
Rebrand Hideout: "Spotting a secret door from a distance of no more than 10 feet without actively searching for it requires a passive Wisdom (Perception) score of 15 or higher, whereas a character who takes the time to search the wall can find the secret door with a successful DC 10 Wisdom (Perception) check." (Phandelver, pg.20, my emphasis)
Cragmaw Castle: "Spotting the tripwire requires a passive Wisdom (Perception) score of at least 20, or a successful DC 10 Wisdom (Perception) check if the characters are actively searching for traps in the area." (Phandelver, pg.36, my emphasis)
The latter makes a lot of sense to me - a character focusing their attention (active check) should gain some sort of benefit over a character who might simply happen to notice something (passive). I like this a lot, if anything because it seems to help assuage the desire to keep both active and passive Perception relevant.
- Firstly, are there any rules (or just reasonable) reasons as to why this doesn't seem to remain consistent in the published adventures?
- Is there a standard (official?) way to determine what the DC difference between the active and passive checks should be when designing my own Perception situations?