Originally, long ago, when you zoomed in, your transparency would not change unless you were in first person. The current version is that it will become more transparent as you zoom in once you are past a threshold.
To get the original version:
1. Get the CameraScript by doing...
A.. Hitting Play Solo and go to StarterPlayer -> StarterPlayerScripts -> CameraScript, and copy/cut and paste it
B. Downloading this XML and inserting it: https://github.com/ROBLOX/Core-Scripts/blob/master/PlayerScripts/PlayerScriptsPlace/StarterPlayer/StarterPlayerScripts/CameraScript.rbxmx
2. Go to the CameraScript -> Open TransparencyModifier
3. Replace line 174 (below)...
child.LocalTransparencyModifier = transparency
child.LocalTransparencyModifier = (transparency < 1 and 0 or 1)
4. Make sure it is in game.StarterPlayer.StarterPlayerScripts
Hopefully not too hard. Enjoy in case you want/need this or a way to override the behavior.