CA Process

In my last post i explained Chromatic Abberation. Well i did have enough time to go through how to actually do it.

Adding Chromatic Abberation:

2D Addition

I've made a rough composit of a CA process on a still, mind you this process is more manual than i usually use, also i base it more of a shot by shot basis. I have a Gizmo i use in nuke that saves me a large amount of time.


The reformat simply changes the format so ignore that. Basically each shuffle node pulls out the seperate rgb channells. Then the red and blue channells have a god ray applied scale, after this ive merged the channells, so first red and blue then merge the red/blue to green.

The result is very slight, but it helps add to the subtle edges to the image.



3D Addittion

Now this is slightly more tricky. So start by setting up 3 different renderlayers RED/GREEN/BLUE. Render your image with its intended Refractions, this is now your green channell. Now, increase the IOR (Just remember to note down your IOR) of your reflections (a small amount is all that is needed, but you'll need to play with your settings yourself) this will be your red channel. Lastly reduce your IOR from the FIRST IOR, this last channell is your blue.

Your results should looking something like this.



Now to display how to easily merge the 3 channells. Ive decieded to add all the channells to black, but this can be done easier (this uses more nodes than it needs).


The shuffle pulls the r,g,b channels out of each of the images. and then they are merged over black.


This merge method is a little bit lighter on the nodes but also simpler. The first merge adds blue too green, then the second merge adds red to blue/green. Overall the result is the same.


Left: Chromatic Abberation Refraction - Right: Standard Refraction


Once again the result is quiet small but the overall effect helps tp sell the shot. These effects can be replicated in AE and any other compositing software. Hopefully this answeres any questions....

Aberration Chromatica

When it comes to compositing its important to remember everything or near enough to everyhting.

Chromatic Abberation (CA) is one of those everythings...

What is Chromatic Abberation:
Basically CA is colour of light waves being refracted different. You are probably not aware but light is treated differntly when it passes through objects but is does, you just need to look at a diamond or glass prism.

Notice in the diamond how faces are refracting different colours, while the glass prisms caustics reflect from red through to blue.

Youre probably thinking where this comes into compositing, this effect doesnt just affect 3D glass refractions. The lens itself is also refractive (go figure....) and the lower quality the lens the more CA is caused (this is why CA is more common in camcorder lenses than in DSLR's). When the light is focused through the lens and the colours refracts to a different area on the CCD. CA is also most noticable when there is contrast between light and dark, similar to light wrap. Light wrap and CA are a great combo.


This diagram kind of explains the effect of CA

How do i replicate it?
There are a few plug-ins and scripts out there, but like with most effects you dont always have access to them and you are kind of left short.

When doing this type of effect you simply need seperate the channels out then radial/direction blur the blue and red channels, and lastly re merge the channels... Quiet a really easy process.

What about 3D?

Yeah what about 3D!
Now with some renderers you can have the option to choose dispersion with refractions. This will slightly alter the IOR of the indavidual channells. If your renderer doesnt have dispersion option you'll have to go old school on it. You render your reflections with slightly different IOR's then in post merge the different rendering into the red/blue channels (also bluring my be needed to help blend).


Conclusion
Chromatic Abberration is by far the best way to add that little extra something to your renders/composits, But you need to use it lightly.

Do not pass GO. Do not collect $200...

Well Ive started over...
The renewal for my website as come and gone and i decieded not to. I think i can use a blog easier, this will help with the updating... Between Blogger, Flickr and Vimeo i should be able to update everything.
Ive got a few projects im playing with, and we are working on a few things at work also.
But ill try and keep the updating going.
~Macky