Panoramic Cameras Wall vs Ceiling Mount
By Ethan Ace, Published Jul 12, 2016, 12:11pm EDT (Research)Panoramic cameras are almost always ceiling mounted, looking down for a general overview of the scene, but is this really the best location, or can wall mounting provide similar or better details and overview?
To find out, we shot out panoramic cameras in two scenes, indoors and out:
Inside, we see how mounting style impacts performance and answer the following questions:
- Which mounting style provides better facial details?
- How does overview performance differ?
- Does either mounting type waste significant FOV area?
- How do software and hardware dewarping impact these issues?
Summary
Wall mounting panoramic cameras provides better details of choke points (main entries/exits or thoroughfares) than ceiling mount while still providing good overview of the scene. However, objects opposite the camera (along the far wall of a room, for example) are delivered in less detail than ceiling mount due to increased distance. Additionally, wall mounting wastes significant portions of the FOV on ceiling/sky.
Ceiling mounting cameras provides worse details at choke points than wall mount, as its higher angle of incidence reduces facial details. However, this mounting style may provide better overview if activity is spread throughout an area, instead of a single key area (e.g., parking lots vs. conference rooms).
Technical Findings
Here are our key findings from this test:
- In our tests, wall mounted panoramic cameras better captured facial details due to their closer position to targets.
- Ceiling mount cameras produced worse subject details due to their high angle of incidence at close range, even when PPF is high.
- Both mounting types provided similar overviews of activities in the scene, though ceiling mount cameras may see over or past obstacles seen in wall mount cameras.
- Wall mounting panoramic cameras potentially wastes significant portions of the field of view on sky/ceiling and ground/floor.
- Using tilt mounts for wall mounted panoramics decreases this wasted area, though not all manufacturers offer these mounts.
- Client side dewarping may offer the ability to eliminate these wasted areas from the scene, but the full stream is still transmitted/recorded.
Test Scenes
We tested in a medium size conference room, with the camera placed in two locations shown on the plan below. The wall mount location was chosen specifically because it was near the main entrance/exit in the rear of the room.
We also tested outdoors, with the wall mount camera again near the main entrance of the building. When "ceiling" mounted, the camera was located midway between the edge of the parking lot and entrance, in a logical position for a light pole typical of many locations.
Wall Mount Better Facial Details
Wall mounting the camera potentially provides better facial details than ceiling mount due to its shallower angle of incidence and ability to locate it nearer entrances/exits.
For example, in this scene, the subject passes near the camera as he enters the room, providing strong details (~120 PPF). However, with the same camera mounted in the center of the room, PPF drops dramatically to ~30, with facial details barely visible.
The comparison below shows subject details from both cameras as he exits the room past the wall mount camera, and as he enters in the ceiling mount:
Similar Overview Regardless of Mounting
In our tests, both mounting styles provided roughly similar capture of general activity in the scene. For example, in the clips below, both cameras easily capture our subject moving across the front of the building and into the main entrance door.
First, in ceiling mount, he moves across the "top" of the image in a dewarped 180° panorama.
When wall mounted, he is clear as well, though details are much clearer as he nears the camera:
Note that in some cases ceiling mount cameras may provide better overview, as they are better able to see over/past obstructions. This may be useful in areas with shelving or crowds of people.
Wall Mount Wasted FOV
Wall mounting panoramic cameras wastes portions of the field of view in many cases. Since the camera's lens "sees" in all directions, portions of the image will be viewing the sky or ceiling and ground or floor, seen in the example below. By contrast, mounting the camera horizontally eliminates most of these wasted areas.
The effect was similar, if not more pronounced, inside:
Camera Side Dewarping Reduces Wall Mount Waste
However, cameras which send dewarped panorama streams may eliminate some or all of these areas by cropping the FOV to more usable areas when wall mounted. For example, the two streams below show camera side dewarped 180° panorama streams from two different cameras. The camera on the left crops some ceiling/floor areas out of the image, while Camera B reduces the vertical FOV even further.
Flat vs. Angled Mounting
Note that in some cases area below the camera may be of interest, to detect subjects very near the camera, objects left or removed, etc. In these cases, angling the camera down may be desirable, and some (though not all) manufacturers make accessories specifically for this application.
When the above cameras are angled down ~15°, unusable ceiling area is further reduced and the area nearer the cameras becomes more visible, including the tables along the wall (mostly out of view previously).
Software Dewarping Flexibility
Client side dewarping may allow users to adjust wall mount panoramas to eliminate wasted areas. For example, in the clip below, we adjust this view in Network Optix NxWitness, removing the sky seen at the top of the image by default and displaying more area beneath the camera.
More On Panoramic Cameras
For more reading on panoramic cameras and their related issues, see:
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