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Fake Chromatic Aberration


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#1 tntman

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Posted 12 November 2008 - 05:33 AM

Anyone got any tips to do/fake chromatic aberration in fusion, I'm looking for some input on how to do it the "right" way and in combination with DOF etc. http://en.wikipedia....atic_aberration

I have tried some stuff like moving or scaling the Red and Green channel of a image and mask it with a Z-depth pass to get chromatic aberration in the out of focused parts and add some grain that is masked with the z-depth too plus normal DOF... all this to get a more realistic final image.

Please write how you adress this area of compositing :)

#2 redoddity

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Posted 12 November 2008 - 05:49 AM

Anyone got any tips to do/fake chromatic aberration in fusion, I'm looking for some input on how to do it the "right" way and in combination with DOF etc. http://en.wikipedia....atic_aberration

I have tried some stuff like moving or scaling the Red and Green channel of a image and mask it with a Z-depth pass to get chromatic aberration in the out of focused parts and add some grain that is masked with the z-depth too plus normal DOF... all this to get a more realistic final image.

Please write how you adress this area of compositing :)


Theo uses this a lot and has some macros that show you how to do it (lenz whore being one of them), but you can easily create it with either a couple of transforms that single out a single channel, or use a directional blur set on zoom. (You can even use the SMeeHee plugin)

see example below (just plug an image into the first directional blur node)

You can offcourse use some edge filtering on highlit or blown out areas to just affect those areas.


copy paste :

{
Tools = ordered() {
DirectionalBlur1 = DirectionalBlur {
CtrlWZoom = false,
Inputs = {
ProcessRed = Input {
Value = 0,
},
ProcessGreen = Input {
Value = 0,
},
Type = Input {
Value = 3,
},
Length = Input {
Value = 0.0226519,
},
},
ViewInfo = OperatorInfo {
Pos = { 660, 214.5, },
},
},
DirectionalBlur1_1 = DirectionalBlur {
Inputs = {
ProcessRed = Input {
Value = 0,
},
Type = Input {
Value = 3,
},
Length = Input {
Value = 0.0171271,
},
Input = Input {
SourceOp = "DirectionalBlur1",
Source = "Output",
},
},
ViewInfo = OperatorInfo {
Pos = { 770, 214.5, },
},
},
},
}

#3 SecondMan

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Posted 12 November 2008 - 05:58 AM

Krokodove comes with a tool called Channel Shifter which can be very helpful for that as well.

#4 tntman

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Posted 12 November 2008 - 06:20 AM

cool will try it all out :]

#5 tntman

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Posted 12 November 2008 - 07:12 AM

Theo uses this a lot and has some macros that show you how to do it (lenz whore being one of them)


Who is Theo and where can I find his macros like "lenz whore"?

#6 marc

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Posted 12 November 2008 - 07:25 AM

I used slight chromatic aberration in the comp that I just published on VFXpedia and here in the forum. It's the method described above.

As far as I could see, lenzWHORE only "aberrates" the optical artifacts, not the base image.
Check out Theodor Groenebooms homepage for some nice macros (and outstanding work).

Marc

#7 protean

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Posted 13 November 2008 - 05:01 AM

I'll maybe post my macro later once it's done.. I just have to figure out wha tto do with the Z-depth channel and it should be complete :)

While I was creating it (using custom tool) I fouind this site very useful:

http://www.vanwalree.com/optics.html

#8 tntman

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Posted 13 November 2008 - 06:47 AM

great info :D

#9 protean

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Posted 13 November 2008 - 10:54 AM

here's a quick comp using the custom tool to shift channels... based on Zdepth (booleaned to RGB).. and also a mask to emulate worsening shift near the edge of frame.

Attached Files



#10 robocop

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Posted 09 December 2009 - 07:18 AM

here's a quick comp using the custom tool to shift channels... based on Zdepth (booleaned to RGB).. and also a mask to emulate worsening shift near the edge of frame.


thanx protean! cool realisation!

#11 protean

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Posted 09 December 2009 - 07:33 AM


here's a quick comp using the custom tool to shift channels... based on Zdepth (booleaned to RGB).. and also a mask to emulate worsening shift near the edge of frame.


thanx protean! cool realisation!



np.. Hmm it's over a year since I posted this so I'd use some sort of deep pixel blur over individual channels rather than this method now :)

John

#12 robocop

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Posted 09 December 2009 - 08:10 AM

np.. Hmm it's over a year since I posted this so I'd use some sort of deep pixel blur over individual channels rather than this method now :)

John


mm .. can you, please, demonstrate this trics ? i`m not clearly understood.

#13 protean

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Posted 09 December 2009 - 10:15 AM

mm .. can you, please, demonstrate this trics ? i`m not clearly understood.


I know I'm being fussy but if you look at the Longitudinal aberration here:

http://toothwalker.o.../chromatic.html

you'll see how it's a bit different to the the commonly seen method of aberration (transverse).

So instead of the channels being shifted they are slightly out of focus which can give the often seen 'purple fringe' effect. You could just scale the channels instead of blurring I suppose or use a combination of both.

I will admit that transverse aberration looks nicer :)

John

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#14 robocop

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Posted 09 December 2009 - 11:09 AM

oowh! great mini tutor!

#15 Tilt

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Posted 09 December 2009 - 11:46 AM

Krokodove's Lens Distortion tool, if used with different values on the red and blue channels, creates a nice aberration as well. It doesn't shift or scale the channels but creates a radial distortion that gets "worse" towards the corners. It's quite close to reality because I have used it successfully to remove aberration from a film scan :-)




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