Both can be used, but “fog on your glasses” is usually a better analogy for darshanāvaraṇīya karma than “fog on a window.”

Reason in simple Jain terms:

• Darshanāvaraṇīya karma = perception‑obscuring karma.

It does not damage the soul’s power of seeing (darshan); it only covers or blocks its expression.

• Fog on glasses:

- Your eyes are fine, but your seeing is disturbed because something close to you is clouded. - Clean the glasses → vision becomes clear again. - This is closer to how karmic particles near/around the soul obstruct its natural perception.

• Fog on a window:

- Suggests the outside object or the world is unclear or faulty. - But in Jainism, the world/objects are not the real problem; the obstruction is due to karma associated with the jīva itself.

So, as an analogy for darshanāvaraṇīya karma, “fogged glasses” (or dust on a mirror) fits Jain doctrine better than “fog on a window.”