Getting very bad results with Position Pass and Depth of Field in After Effects

[Xavier Bonet]

Man, this is the kind of empirical wisdom I wish I would always get when I come here with an issue! Clearly you’ve been through these 3D existential doubts before and to get a glimpse of your workflow is much more valuable than just getting a quick solution or workaround for one specific issue.

I don’t do much photo-realistic work (just play around with it for my own amusement), so I’ve yet to be able to justify the expenditure of getting Octane, Redshift, etc. But every time I watch a tut that uses them I want them!

This weekend I had a lull in my work, so I decided to go ahead and update to C4D r25. As I feared, they’ve changed things around quite a bit! So that’ll take me a couple of weeks of slower workflow before I get the hand of stuff. But I’m hoping there are some improvements.

[Xavier Bonet]

Steve, can I further pick your brain? What do you do in terms of Pos Pass when you use tele cameras? When working with a sort of isomorphic aesthetic, I find that the only thing that gives me control is to use a camera from 135mm up. And when I really need to crank it up in order to get a very flat effect, there’s no way I can get the Pos Pass to work correctly…

[Steve Bentley]

Hey, sorry – been on a deadline before we shut down for Covid again.

Will get you that AE file shortly.

As for lens lengths – the longer the lens the larger the aperture values or less DOF you can use to get results. But you can get extreme DOF with any length lens (these are virtual lenses after all so you can break physical rules). Setting the aperture to 0.1 or lower is not unheard of to get good bokeh with a sub 100mm lens.

There is no real world lens with that kind of F number (I think 0.95 holds the record right now), but there’s no reason you can’t make the math in 3D work for you.

So that’s from a true DOF work flow.

For POS passes, don’t forget you can use a non perspective camera, there are Parallel cameras, isometric cameras (probably this one) and diometric cameras selectable in the object tab of the camera object. They can be a little weird to work with because no matter how close you get them to the object the objects don’t get any bigger. Its all about the zoom in the view port. (in Arnold they are called Ortho cameras)

There should be no difference in the POS value because that’s a spatial calculation separate from the lens. But to be fair it’s never come up – I’ve just used the lens I need (and because motion picture film/sensors have a smaller frame size it’s rare for you get into long lenses – a 150mm would only be used for extreme telephoto – the crop factor, depending on sensor size or say a 4 perf film frame, that would be equivalent to about a 250 or 300mm on a 35mm SLR. If it’s one of those kinds of shots – the battlefield kind of zoom in to find the hero – you are cheating the focus all over the place so a POS pass wouldn’t even be rendered ).

I will give a long lens a test with POS and see what happens.

[Steve Bentley]

I just thought of something re your blooming edges – the POS pass must be rendered without alpha.

And, are you working in a 16 bit or 32 bit AE project? These two items are essential to hold all the data from the EXR.

And (I’m just doing this from memory looking for things it might be that slip people up), don’t you have interpret the POS pass footage in AE as having no color management or setting it 32 bit linear?

Also in the POS pass settings, you should not be using the world space but camera space – this way the Z depth recorded in the Blue record of the EXR is always away from the camera even if the camera is pointing left or right or up or down.

[Tariyel Seyidov]

Hello. I myself encountered this problem in the After Effect and looking for a solution to the “halo” problem on the Internet, I found nothing but to use the Frischluft Lenscare plugin.

Here is my solution to this problem:

Available render and z-depth render.

I separate the top sharpnessed layer. And at the bottom blurry layer, I displace the edges inward like effect contrary “bulge”.

Pre-create an additional layer of zdepth with a small blur (Fast Box Blur =3). We call this invisible layer “blurZdepth”

1. The upper sharpnessly layer is separated from the lower layer using the “set matte” effect (layer zdepth, luminance). 2. Then on back layer for blur we put two “displacement map” effects with our map layer “blurZdepth” and one “your blur”* effect on the layer with your parameter equal to the number =N. The first “displacement map” with a parameter equal =N (delete halo around left and top). The second with the parameter (minus) – N / 1.5 (delete halo around right and bottom).

* On both layers (upper sharpnessly and lower blurry), you can install a “Camera Lens Blur” with the desired settings for the texture z-depth.