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z-depth with fast blur? alternatives to lens blur map channel
Hi
Is there anyway to use a z-depth render with faster types of blur than lens blur?
I have to render the z-depth tif sequences seperately because of a mental ray render bug so I cannot make RLA/RPF files and use 3D channel depth of field plus there is no way to join a z-depth channel with a normal channel into a RLA file later.
Currently Im using lens blur with a z-depth map in the depth map channel but its really slow and not very tight. I would like a very short depth of field and when i turn up the iris radius it doesnt change the shortness of the DOF,ie tightness, it just increases the blur amount plus its VERY SLOW.
this subject has not been discussed much so any help greatly appreciated.
thanks a lot
joe ger
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4 Replies
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Compound blur renders much faster than Lens Blur.
Most of the time, unless you have a very large scene with lots of distance between the foreground and background objects, your z depth pass will not have much contrast and will probably look mostly white or grayish.
This doesn’t give the blur effect much to work with so when you crank up the blur level it just appears to blur everything.
One way to get the exaggerated DOF you are looking for is to apply a Levels adjustment to the z depth map layer to increase the contrast between the light and dark areas. Then pre-comp the layer and select “move all attributes”.
Now select the z depth pre-comp as your Blur Layer in the Compound Blur effect and turn up the blur level (you may need to check Invert Blur).
Hope that helps.
-E
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Thats a good idea and thanks a lot for the detailed answer. I will give it a try now
Joe Ger
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My plan was to blur both the edges of my shot not just one end. I will have to fiddle with it to make it do that
JG
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Joe, The reason only one end of my example is blurred is because that’s the end that’s farthest away from the camera. The distance of the objects in the scene is what determines how blurred they will appear based on the information in your depth pass.
If the 3D Text was facing the camera straight on and it was centered in the frame and there were other objects in the scene behind the text at various distances then the text would be in focus and all of the objects behind the text would be blurred according to how far away they are from the camera. Make sense?
Let me know how it goes.
-E
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