yea, I've jsut started using depth of field a bit, to save a
bit of photoshop work w/ adding a nice fade to black background.
But, it seems like changes i make to the indirect illumination (
the amount of it) in the environment tab of the scene editing
window, make to difference. how does DOF work with indirect
illumination? thanks
Introduce Depth of Focus surely will affect the indirect illumination ( or to be more precisely, will darken your scene), this is very natural, as it needs to follow the theory of photographing.
Imaging you are using a camera, (PhotoWorks brand), when you need to define a focus point with certain area of DOF, how the PhotoWorks is going to achieve this effect? it will try to reduce the aperture or shutter speed - >both will result in lesser light to expose your PhotoWorks film, so, naturally, if you need more DOF effect (narrow down the DOF range) , your scene will become darker, and you have to compensate it manually. (increase no. of light bouncing , or increase the light source brightness)
Below is something I copy from Maxwell Render website. Just for your reference. I found out it's quite useful for Photoworks users as well.
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DOF Theory
When you focus on a centric element in your image, areas that are out of focus typically become unsharp. This phenomenon is called Depth of Field (DOF).
DOF Practice
The DOF amount depends on the fstop (An important notion in optics, fstop expresses the diameter of the entrance pupil in terms of the effective focal length of the lens. fstop is the quantitative measure of lens speed in photography. The smaller the fstop, the smaller the DOF, meaning only a small area of the image will be in focus.) value and the lens diameter, so the Focal length dictates the amount of DOF. Decrease the fstop value and/or the lens diameter for a more exaggerated contrast between areas that are in focus (sharp) and areas that are out of focus (blurred).
I don't believe that PW works like a camera. Where is our setting for shutter speed? By defualt PW does not take into account DOF. Everything is in sharp focus. If we followed the camera metaphor, then we would have the equivalent of a pinhole camera and massive amounts of light would be needed.
An interesting tool here:
http://think.maxwellrender.com/dof_cue_tool-111.html
A very good article here: one thousand times better than mine explaination:
http://en.wikipedia.org/wiki/Depth_of_field