Lens Effects Gizmo + Goals

As part of my ongoing compositing development for Big Top and Dino Diner I have compacted the lens effects node tree I made before Christmas into a Gizmo.

The fundamentals of each different lens effect come from this tutorial which I have modified, below I've got a screenshot of it being used for a character AOV test in The Big Top.


The effects the gizmo is currently capable of are:

- Depth Of Field

- Vignette

- Filter Flare

- Lens Distortion

- Field Curvature
(Edge defocus)

- Lens Flares

- Glow

- Chromatic Abberation
(Axial and Traversal)

- Grain

The user is able to work their way down the list of lens effects enabling or disabling them, and tweaking as they see fit. The aim being to allow people to more easily add real world lens effects to the perfect CG renders.

This was roughly the node tree I started with, I ended up leaving out Astigmatism as I think the effect had to much of a dramatic impact on image quality.


Creating the gizmo was a simpler process than I was expecting, being able to pick the necessary controls from the node tree was very intuitive, and meant I could give the user only the necessary dials and sliders for the optimal amount of control. I spent a long time organising the layout into a simple and easy to use set of drop down menus for each effect.

For some aspects I felt like the user needed to see results from within the node tree to get a better idea of what was going on, for example the filter shape of the vignette, or keyer selections for the filter flares. For this I used the switch node tied to a drop down menu on the gizmo. This allows the user to view specific parts of the tree to see better what they are adjusting.

 So far feedback from the gizmo has been good and I have been able to make good use of it in my work.

 Here's a before and after of the lens effects on an R&D comp for Dino Diner, making main use of depth of field, glow, which can be seen on the table, field curvature and chromatic aberration around the edges, grain and slight amounts of filter flare, which can just about be seen in the light shaft.



The effects here are quite on quite strong, especially depth of field, but you can see when they come together it does make you feel like you are looking at a more traditional photo, and makes for an overall more pleasing image.

Appropriate Effects
My end goal is to apply more of my camera and lens knowledge into the way the user interacts with the gizmo, advising them as to what type of effects you would be likely to see in the real world based on the image you are working on.

Dark Scenes
For example, shooting darker scenes is harder for a camera, so the options are to increase ISO, widen the aperture, or add additional lighting.
Widening the aperture (lowering the F-stop) allows more light through the lens, but often increases effects like chromatic aberration, vignette and Depth of Field.
Increasing the ISO increases noise, or on film stock would increase the amount of grain, on the image.
So if the compositor is working on a darker shot, this is the type of lens effects you would be looking to add.

Brighter Scenes
On the other hand, to remain properly exposed on bright exterior shots you would be looking to close the aperture (increasing the F-stop) and/or potentially use a Neutral-Density (ND) filter, which in turn may lead to flaring caused by the extra glass filter on the lens. But you would expect to see less aberration, vignette and depth of field.

You may also have specific lenses for specific jobs, each would have their own individual qualities, such as a unique amount of lens distortion, or how strong aberrations can be.

So what I aim to create in the long run is something that will help the compositor decide what lens effects would be present based on the overall brightness of the image. 

I may also pre-create a digital lens collection or rough guide for focal lengths to keep a consistency throughout Dino Diner, and an accompanying preset gizmo for that lens.

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