Skip W., via WoTC website wrote:Disbelief: A successful save lets a creature ignore the effect. Spells that allow this kind of saving throw usually are from the illusion school, and they usually don't have any direct effects on creatures or objects, but instead have effect or area entries. Creatures make their disbelief saves upon interacting with the area or effect in some fashion. The rules don't give any guidelines on what kind of interaction is required. As a rule of thumb, a creature interacts with something upon attacking it, studying it, touching it, talking to it, or doing something else that one might do with a real creature or object. Merely looking at something usually doesn't qualify as interaction, but using an action (standard or full-round) to study or identify it does. Sometimes a disbelief save is automatic, such as when a character tries to touch an illusory wall and his hand passes right through it (see page 173 in the Player's Handbook for details).
Silent image is a good example of this kind of spell.
So with this clarification, you now can automatically pass a save when any part of the illusion is wrong (like noticing that the illusionary Silent Image goblin is not making sound, even though some other effect like Silence could be making the goblin quiet.)
The example of "passing your hand through an illusionary wall" equals free disbelief also ignores the fact that in a wild and wooly magical world, there could be any number of effects that create a wall that you could pass through.
People also get saves every round they talk to a guy with Disguise Self on.
I wish Skip would get fired or something.
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Luckily, you won't get a Spellcraft roll to automatically know that the spell is a Silent Image. You only get that with a Negate save spell.
As above wrote:Negates: The spell has no effect on a recipient who makes a successful saving throw.
If the spell has no obvious physical effects (and most spells that allow saves to negate don't), a recipient that makes a successful saving throw still feels an obviously hostile force or tingle. If the spell has a target or targets entry, the caster knows that the spell has failed.
A recipient who makes a successful saving throw doesn't know where the spell came from (though that might be obvious if the caster is visible) or what the spell was. If the spell has a target or targets entry, however, a recipient that makes a successful saving throw can attempt a Spellcraft check (DC 25 plus the spell level) to determine what the spell was. This does not take an action, and the recipient cannot retry the check if it fails.
Charm person is a good example of this kind of spell.
