Make window a specific size on screen regardless of camera size

[technoir]

I have a camera which zooms into a set of buttons, which when clicked, cause a window to open in the foreground. I would like to know how to make sure that the size of the window on the screen is the same (regardless of the camera's orthographic size). So, for example, if I choose not to zoom into the buttons (so cam size = 1), then the window that opens is the same size on the screen.

Any guidance/tutorials would be great - Thanks.

[ArenMook]

The first question comes to mind is why would you zoom the UI camera? UI camera should be separate from your game camera. Zoom the main camera all you want, but don't touch the UI camera.