Can a spell detect the invisible?

[OneShot]

The critical misunderstanding happening often is, that moving or destroying an image of a thing just involves affecting the species it emits. This is not the case.

Note that (HoH:S p.61)

Iconic species are carried in light

and Imaginem does not affect light: this is the domain of Ignem.

EDIT: See also here.

As Imaginem affects images, the resulting handling of species is sometimes tricky - and shadows are beyond its power.

@Gaxxian

Perdo means Perdo, not Muto. You aren't changing species but destroying them. And you can't detect altered species where there aren't any.

Such an Invisibility spell is easy to invent but would fail its purpose: no need to publish it. Just destroying the species it emits leaves a featureless shadow standing around: anything but invisible. Destroying a visual image involves moving iconic species around the object made invisible.

@Gaxxian

Also, when somebody uses a ReIm to move your image to a distance, in the original spot the real caster remains invisible, not a lightless hole.

Quite. So again ReIm - moving images - does not just move your iconic species away: it moves others in.