Auto air filter - what are the visual clues to replace it?

Question

How can I tell when my car's air filter needs to be changed? It's not buried under under an inch of dust - but there is a light film of dust on all the surfaces. Are there any photos out there that will teach me to tell the difference between fine and replace?

Answer 1

the way i tell,is that i hold it up to the light and if i cant see light through it,then i replace it,also you can roll it around a trouble light too.

Answer 2

I replace mine once a year or every 12,000
miles.
Its cheap prevenitive maintence.

Answer 3

Can you see sunlight through it?

No?
Replace it.