I've seen a lot of people struggling with getting proper Z-depth passes out of 3DS Max. I've been struggling for hours with getting decent Z-depth information embedded into my EXR files in renders from both AOV Arnold renders and with the Z-depth buffer added to common-file EXR renders. Most of the suggestions in the manual simply don't work for me.
I finally found the solution in a Cinema-4D forum, of all places. It's pretty simple.
1. Do not embed a Z-depth buffer into an EXR file whether as the "Z" element to an AOV file or in the common-file renders with the Z-Depth buffer added. Neither way worked for me.
2. Working through AOVs, render out an AOV with JUST a "Z" pass. Render your beauty, other channels as a separate AOV pass.
3. In After Effects when you bring in the Z-channel-only render it will be all white. That's what you want. Apply the Extractor effect to that layer. It will turn all black. In the drop down box next to the Red Green Blue channels, change them to "Y". That's luminance.
4. Adjust your black point until you get a gradient on the image from near (light) to far (dark).
Hope this works for you. It did for me.
