so, here is a weird thing that sometime happens, the Z-depth become too dark sometimes. I don’t know what’s causing it, but I managed to capture it perfectly. I was testing that question in certification exam about “can you get z-depth channel while rendering z-depth” 
and this is the result:
here is the z-depth I chose (main render)
and here is the Z-depth channel:
it has happened several times to some of my renders. any one knows why?
Hello @DynamicRenderLabs,
Thanks for reaching out.
I suppose this issue is caused by the difference between the Z Depth in Style and the Z Depth Channel of the output. The outputs of them could be different.
The Z Depth in Style is a post effect that is overlayed on the current preview image, if your current preview image is bright then the output will also be bright. The Z Depth Channel, on the other hand, does not involve an overlay, it is a standard z depth map, a greyscale map that depends entirely on the distance from the object to the camera.
If you are thinking the Z-depth channel is too dark, you can adjust the slider. For details, please refer to this post: How is Z Depth used in Style? | User Manual (d5render.com)
