# DOF with a mirror?

I am working on a Medusa scene where she is staring into a mirror. We are looking at her from behind, looking into the mirror.

I want to use DOF, However if you look closely the mirror is completely in focus (the grunge is tac sharp) but her reflection is blurry.

How do I get around this?

• Cycles is quite physically accurate, but I'm not sure if it can deal with reflection based DOF, you might have to do it in compositing – Duarte Farrajota Ramos Aug 2 '18 at 16:14
• Actually it does, ill post an answer shortly – Duarte Farrajota Ramos Aug 2 '18 at 16:18

Say if an $$Object A$$ is at 2 unit from the reflecting surface $$Mirror$$, and the mirror is at 4 units from the $$Camera$$. Then a ray traveling from the camera to the "object reflection" will have to travel the cumulative distance from the $$Camera$$ to the $$Mirror$$, plus the distance from the mirror to the reflection beyond it.
This would be equivalent to the cumulative distance from the camera to the mirror plus from the mirror back to the object, hence $$2 + 4 = 6$$, which would give us the correct value to insert in the camera Focus Distance parameter of the camera.