cromatic aberration in post

[leif3d]

There are many tools for doing chromatic aberration in Post. It's a simple channel shifter really...
You'll obviously have to deal with the fact that it's a cheat and not really a physical solution in any way when doing this in Post.

I've done this a many times and I have yet to meet one person than can tell the difference...now that I think of it, I don't remember ever meeting a person that doesn't do chromatic aberration in post.

What compositing application are you using?

[tharrell]

Super easy way to do it in post:

- Isolate and mask your item
- Split the object into independent RGB plates, and offset each by a couple pixels, usually triangularly
- Maybe blur the most dominant channel a little
- Grab a key off a highlight or bloom spot (assuming you're doing aberration on a highlight)
- Apply key alpha to your reassembled stuff
- Comp

Or, just grab Sapphire or one of the Tinderboxen. Forget which :)

--T

[leif3d]

Good tips Trey.
Also remember that chromatic aberration is stronger on the edges of the frame and a lot subtler on the middle.

[royterr]

There are many tools for doing chromatic aberration in Post. It's a simple channel shifter really...
You'll obviously have to deal with the fact that it's a cheat and not really a physical solution in any way when doing this in Post.

I've done this a many times and I have yet to meet one person than can tell the difference...now that I think of it, I don't remember ever meeting a person that doesn't do chromatic aberration in post.

What compositing application are you using?

Then what's the advantage of doing this in Maya?
Is it more accurate like 3d motion blur in maya compared to a 2d motion blur in post?
If it's a simple post effect why does it take crazy time in maya to render?
is it because it's doing DOF at the same time?

[tharrell]

Ohh... are you using the mia_lens_bokeh to do your DOF and aberration? It's sounding like you're really interested in bokeh effects, not so much shifting your color channels around a lot (what most people think of chromatic aberration). The shift is a part of a bokeh, but it isn't as pronounced as what I generally think of an aberration effect.

Depth of field is really really painfully slow in MR... basically when you have to crank up the samples to 16 to smooth out the grain, you're multiplying your render time by 16. Gross simplification, of course, but it's not too far off from reality. Other depth of field controls in MR have similar performance hits.

It looks awesome though if you can afford the render time.

If you're doing motion blur as well, try changing to the rasterizer engine -- it'll speed stuff up quite a bit, and motion blur almost always looks better if you can render it in your plates.

But my advice would be -- do both your DOF and aberration as a single operation in post... have you looked into DOF pro? As long as you can get a Z-depth pass, it's pretty awesome:

http://www.dofpro.com/overview.htm

Even the lens blur filter in Photoshop / After Effects looks pretty good these days too, although the bokeh doesn't look as nice.

--T

[tharrell]

Also if you haven't played around with using mia_lens_bokeh to do what you're wanting, give it a shot (it does DOF and distance aberration) and apply the attached thumbnail as a bokeh texture.

But remember, it's sloooow once you turn up the samples to get a smooth result.

--T

[royterr]

Ohh... are you using the mia_lens_bokeh to do your DOF and aberration? It's sounding like you're really interested in bokeh effects, not so much shifting your color channels around a lot (what most people think of chromatic aberration). The shift is a part of a bokeh, but it isn't as pronounced as what I generally think of an aberration effect.

Depth of field is really really painfully slow in MR... basically when you have to crank up the samples to 16 to smooth out the grain, you're multiplying your render time by 16. Gross simplification, of course, but it's not too far off from reality. Other depth of field controls in MR have similar performance hits.

It looks awesome though if you can afford the render time.

If you're doing motion blur as well, try changing to the rasterizer engine -- it'll speed stuff up quite a bit, and motion blur almost always looks better if you can render it in your plates.

But my advice would be -- do both your DOF and aberration as a single operation in post... have you looked into DOF pro? As long as you can get a Z-depth pass, it's pretty awesome:

http://www.dofpro.com/overview.htm

Even the lens blur filter in Photoshop / After Effects looks pretty good these days too, although the bokeh doesn't look as nice.

--T

you mean if i render a zdepth pass i can easily mimic MR depth of field effect?
but it wont mimic correctly the cromatic abberation like in Maya?

[royterr]

There are many tools for doing chromatic aberration in Post. It's a simple channel shifter really...
You'll obviously have to deal with the fact that it's a cheat and not really a physical solution in any way when doing this in Post.

I've done this a many times and I have yet to meet one person than can tell the difference...now that I think of it, I don't remember ever meeting a person that doesn't do chromatic aberration in post.

What compositing application are you using?

i am using aftereffects.
could you give a visual exemple where your chromatic aberation in post look the same as in MR?

[leif3d]

Take a look at Frischluft Lenscare for after effects.

Also take a look at the Sapphire plugins. A mix between S_RackDefocus and S_WarpChroma will get you the effect you want.

After effects has a Lens blur which is very slow, but can also accomplish some decent rack defocus effects.

Chromatic Aberration can be faked by shifting channels. In Fusion this can be done by separating channels and then re-merging them after offsetting them slightly.

For a deeper explanation, you'll have to post in the After effects forums I guess.

[igi]

A tutorial for after effect which I found very useful:

http://ae.tutsplus.com/tutorials/motion-graphics/learn-how-to-create-chromatic-aberration/

[eem]

sapphire plugins has a function that can make chromatic abberation automatically

[royterr]

ok thanks alot guys, i will have to do some tests to see if one can really obtain the same results in AA just like in MR.

[rBrady]

If you are faking it by hand remember that its mostly visible in hotspots that are above 150% white. If you are using HDRIs and comping EXRs then you could clamp down to only include the upper range and apply your effect there. It would be most accurate that way but accuracy may not be what you are going for.

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