Translucent materials, when they are set up to Render BEFORE depth of field, don’t have the right behaviour with the camara focus. This happens at least from 4.27 to 5.21:
This issue is hard to spot as you need a cinematic with depth of field and even that can be hard to realize as the focal point of the translucent materials seems to be moved in space further away. In this example, 2 different materials set to translucent and render Before DOF are exactly 500cm to camera, but they remain blurry.
In order to be in focus, the focal length of the camera is set up to 2500cm, not the real distance where they are.
Another strange behaviour of translucent materials redered Before DOF is that their blurriness is affected by other meshes behind them:
This seems to happen kindy of inversely when they are in focus too:
The areas that overlap with a mesh behind are now blurry (as they should probably because the focal lenght is way longer that where the planes are.
These can be replicated easily with any translucent material I think:
I really wish I could control the blurriness of materials because I mean to use UE for compositing very often and this issue, could be an oportunity too.