and how do I get rid of it? It prevents me from moving around in the camera view.
I highlighted it using the red arrow. When I mouse over it is says, “perspective lens value in millimeters”
It appears after I set a keyframe for the camera. Can anyone tell me how to cancel it? It interferes substantially with my ability to use the “Lock Camera to view”
Thanks for any help 
Is related to the Sensor Fit setting? Changing that to Vertical is the only way I can make a yellow square appear (then changing the height can move it in front or behind the camera object)
Not sure that’s it on my side. I figured out the workaround on getting rid of it for me… (not sure this is the correct USE of 2.8, but here’s what works).
Select the camera, go into Camera view (numpad 0), press G, move around a tiny bit, then you can select another object (if you wish for setting up and centering a scene), and lastly select the camera again and ‘i’ to create a keyframe. HTH others who are having similar problems.
I still don’t know what the yellow rect is for…
What are your Camera setting regarding Sensor Fit? The yellow box is always present for me in 2.8. It’s just normally aligned exactly with the front of the camera. You can click and drag on it to change Focal Length.
Here’s the issue from my point of view:
FILE:
https://filedn.com/lLMW4jXsJqxXkRYjd1UCoKL/3d/sample20eeveePUB.blend
That is puzzling. I can’t get my camera to work like that. You are in camera view, with Lock Camera to View checked: What are you then pressing? R to rotate? Middle-mouse? In both situations, using your .blend file these work as expected with no weird yellow thing appearing.
I used to move my camera around in a similar fashion, until I became addicted to the Fly mode (Shift+F in 2.79, Shift+` in 2.8). I just find it works better for me. The fact I can rotate my camera while moving it left/right up/down at the same time just feels more natural when working out where I want the camera to be.) An added benefit being I can uncheck Lock Camera to View and leave it unchecked.
That extra yellow square is supposed to be a camera gizmo so that you can change the FOV by dragging it.
It seems like it’s currently broken - should be fixed.
Ah… I’m using a build from about 4 or 5 days ago, and I guess it broke between then and now. Cheers William
Funny, I just DL’ed the nightly build last Eve. Not sure what the difference is. IMO, it’s still broken
It’s still broken. What I meant was that it aught to be fixed, not that it is fixed. 
