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Left: Camera target is placed at the third sphere which is also the area where the focus ring is pointing: perfect focus. Middle: Camera target placed too close, Left: Camera target placed too far back.
Moving a Camera
Please see the Viewports and Navigation page for details.
Hidden and Locked Cameras
When editing a camera, keep in mind that you can Hide/Unhide a camera (for a cleaner visualization), or Lock/Unlock it (to prevent an accidental editing) on the Camera Parameters panel of each camera.
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You can choose whether the selected camera should be a perspective camera (3D projection) or any of the 2D orthographic projections (Top, Left, Right etc.)