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Date: Mon, 10 Jul 1995 16:19:35 +0200 (MET DST)
From: "Aljosa Brajdic / Arhitektonski fak." <[e-mail]>
To: [e-mail]
Subject: Re: depth of field
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> Some of You could make a test of this idea.
> Render Your existing scene in RGB.
> Make new scene without lights, ambient 255, camera and all
> objects in same positions. All object should be made color
> 255,255,255 (white), no specularity or reflectivity...
> Now make fog 0,0,0 (black) that begins in distance from You wish
> to lose sharpness.
> Rendered image will look something like base for stereoscopic
> images!!! (If You apply filter Stereo noise from KPT for
> Photoshop You will get one, it works even as animation, but watch
> Your eyes). Load images (color and b&w) in Image processing
> software IMAGEFX(Amiga) or PHOTOSHOP (PC), apply the gaussian
> blur on color image with influence of b&w alpha image(!do not
> forget to g-blur alpha image before doing this!).
> The result should be something like depth of field with one
> problem - You cant make it fuzzy towards camera (the fog does not
> act that way).

This trick looked like it could work, but the result was not very
satisfactory. This was due to the way Photoshop applyes gausian blur on
images with masks. Areas which are excluded from selection are not
affected, but their surrounding is. After a few hours of experimenting, i
found a way of producing satisfactory DOF renderings.

1. Render an image as stated in mr. Dabrovics letter.

2. create mask image with black fog following the same instructions

3. do NOT blur mask image

4. apply gausian blur using mask image more times with lower walues.
   For example: I tried gausian blur with radius 0.5-1 pixels applied
   5-10 times on 320x240 picture. It worked fine!!

5. another problem i encountered was poor DOF simulation. When you focus
   an object with your photo camera, objects in front will be blurred as
   well as those in the back. When using fog to create mask, sharpness will
   decrease linary from camera to the choosen object. To resolve this
   problem you can use CURVES option in Photoshop or similar program.
   Picture in which I explained all this can probably be found on
   TOMAHAWK - DOFAB.JPG (if I found a way to post it), or I can send it
   to you by E-mail if you send me your request.


Aljosa Brajdic
Kataliniceva 2
51410 Opatija
CROATIA - HRVATSKA
[e-mail]
--
"Aljosa Brajdic / Arhitektonski fak." <[e-mail]> sent this message.
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