View Full Version : Faking DOF

02 February 2003, 07:40 AM
Can anyone help me out with a technique for faking Depth of field effect. I remember reading about a technique using black fog, but can't remember how to actually implement it in post. I'm trying to achieve a smooth transition from fucused to blurred objects along the camera plane. I would check the AM mail archive, but it doesn't seem to exist anymore.

02 February 2003, 05:38 PM
Why are you not animating the DOF of the actual camera?

The "black fog" technique, is simply to get you a depth map.

Have all the objects in your scene be matte white, and have the fog be black. Anything that is white will be IN focus anything that is black will be blurred.

Then take a post program like AE or similar and apply the blur to that depth mask.

I still wonder why not use the DOF of the camera? is the results that bad?


02 February 2003, 11:19 PM
Thanks for the info jdates.
I should have explained myself better though. I'm actually working a hires still, not an animation. I want to be able to add DOF to my image without having to re-render the colour passes, which would take a couple of days. A fog pass seems like an easy alternative, which would also allow me to tweak the amount of blur during compositing. I believe the AM camera will produce a sharp change between blurred and focused, when using its DOF. Also, it will not allow one object to be much more out of focus than another. Basically I want control over the DOF, can the fog method give me that?
How can I implement this in a still compositing program (PSP/GIMP)? I don't think thay have depth masks do they?

Thanks again.

02 February 2003, 11:40 PM
You use the depth image as a mask. selection mask in photoshop. this will make everything white selected and everything black excluded. The grays will be effected by any filters based on how light they are. You may have to reverse the picture if this is the case but you should be able to figure out with a little trial and error.

Not sure how it works in psp or gimp.


02 February 2003, 12:43 AM
I just played with PSP so here goes...
open your color render and your depth map render

What you will need to do is select the color render and click make mask from image, select your depth mask image from drop down menu. Then in selection menu click use mask.

Now when you apply blur it will work correctly. if blur is reversed reverse the depth image first then use it ask mask.

I just looked at the program so their may be a faster way to do this but that is the basics of it.


02 February 2003, 07:07 AM
Great! :applause:
Many Thanks.

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