Question/Discussion about DOF physics over reflections.

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posodrac
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Question/Discussion about DOF physics over reflections.

Post by posodrac » Wed Sep 09, 2020 7:25 pm

:hat: Imagine a trees line in the horizon, out of focus zone. Because of the low angle of the camera the top of the trees reflect in a lake in the focus zone.
Question: Will the reflection be blured or crisp?
This will look good in my "curriculum vitae": "Heterodox truck driver at TNT/FedEx"

Fletch
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Re: Question/Discussion about DOF physics over reflections.

Post by Fletch » Thu Sep 10, 2020 7:01 am

My initial instinct is to say that anything that would be out of focus (the trees in your example) would still be out of focus in the reflection in the water. To be clear - the water would be in focus, the ripples in the water or whatever, but the trees would be blurry.

That's just my guess - if we are just playing "thought experiment". :!

This is because you can do this with your own eyes - focus on a reflection that contains a near and a far object, and you can focus on either one, causing the other to be blurry. 8-)

I'm no optics expert. :shh:

Chris
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Re: Question/Discussion about DOF physics over reflections.

Post by Chris » Mon Sep 14, 2020 2:11 pm

I would expect the reflection to be blurred. However, if you are doing a render of this situation and you use the "Depth Render" trick to create your blurred depth of field, you would get crisp reflections.

posodrac
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Re: Question/Discussion about DOF physics over reflections.

Post by posodrac » Fri Sep 18, 2020 7:30 pm

Chris is right. I did the experiment with a mirror and if you stay focused on one point in the mirror the reflected image of the background will always be sharp. Well done Twilight Render code team :hat:
This will look good in my "curriculum vitae": "Heterodox truck driver at TNT/FedEx"

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