What a fisheye camera is, how one camera covers a whole room, what dewarping does, where detail runs out, and when to choose fisheye, multi sensor or PTZ.
One fisheye camera on the ceiling sees an entire room, with no blind spot beneath it.
Detail falls towards the edge of the circle. Plan fisheye for awareness, not identification.
Use the IEC 62676-4 pixel densities to check what a camera can really achieve at each distance.
Pair fisheye with narrow view cameras at entrances, where people are identified.
Always record the full original circle. Flattening only on the camera throws footage away for good.
Test analytics at the edge of the picture, not just the centre where demos are filmed.
A PTZ camera records where it points. A fisheye camera records everything.
A fisheye camera is a fixed security camera with an ultra wide lens, usually covering 180 degrees, that records a circular picture of the whole area around it. Mounted on a ceiling and pointing down, it sees 360 degrees: from the floor directly below out towards every wall. Software then "dewarps" the circle into flat, natural views an operator can read at a glance.
The terms get mixed up, so here is how they relate.
Fisheye camera: one lens and one sensor, producing a circular picture.
360 degree camera: a description of coverage rather than construction. Most 360 degree security cameras are fisheye cameras; some use several sensors.
Panoramic camera: usually 180 degrees side to side, built from one wide lens or from two to four sensors joined together. Usually wall mounted.
Multi sensor camera: several lenses and sensors in one housing, each aimed in a different direction. It covers 180 or 360 degrees with much more detail in each direction.
An ordinary lens keeps straight lines straight. That stops working beyond about 100 to 120 degrees, because the edges stretch further and further and the picture would need to be infinitely large to reach 180 degrees.
A fisheye lens gives up on straight lines. It squeezes a whole hemisphere into a circle on the sensor. Lines curve, and objects near the rim are compressed.
The exact way a lens does this is called its projection. Common types include equidistant, equisolid, stereographic and orthographic, and they differ in how hard they squeeze the edges. It matters because dewarping software has to reverse the projection: if it assumes the wrong one, straight lines in the flattened view come out slightly bent.
Ceiling mounting is the default and the reason fisheye exists. Pointing straight down, the camera covers every direction with no blind spot underneath, which a wall camera always has. It suits retail floors, lobbies, open offices, warehouses with open aisles, classrooms and waiting rooms.
Wall mounting gives a 180 degree panorama of the space in front. It works along corridors and at entrances, though a purpose built panoramic or multi sensor camera usually gives more detail.
Height matters more than most specifications. A ceiling of 2.7 to 4 metres works well. Higher, and people at the rim become tiny. Lower, and the camera is easy to tamper with and sees mostly heads.
This is the part most product pages leave out.
A 12 megapixel fisheye camera does not give you 12 megapixels of detail wherever you look. The lens draws a circle on a rectangular sensor, so the corners go unused. That circle covers a whole hemisphere, where a normal camera covers perhaps 90 degrees. People directly below are closest and largest; people near the walls are further away and squeezed by the lens, so detail falls steeply towards the edge.
The useful measure is pixel density on the person, in pixels per metre. IEC 62676-4, the international standard for applying video surveillance systems, sets widely used reference levels for different tasks.
At 25 pixels per metre an operator can detect that someone is there. At 62.5 they can observe what the person is doing. At 125 they can recognise someone they know. At 250 they can identify the person beyond reasonable doubt.
A good fisheye camera on a normal ceiling detects and observes comfortably across the whole room. It reaches recognition level near the centre. It usually reaches identification level only directly beneath the camera.
So a fisheye camera tells you what happened in the room. On its own, it rarely tells you who did it. The proven design is a fisheye for awareness plus a narrow view camera at each entrance, where every person passes close enough to be identified.
Dewarping turns the circle back into flat views that look like normal footage. There are three common views.
Virtual PTZ: one flat view the operator can pan, tilt and zoom within the circle, like a PTZ camera with no moving parts.
Panorama: the circle unrolled into a wide strip, often shown as two 180 degree halves.
Quad view: four virtual cameras at right angles, shown as a grid.
Where dewarping happens decides what you can do with recordings later.
On the camera. The camera sends flat views only. It is simple, but many cameras then discard the original circle, so the recording holds only the views someone picked in advance. If something happened outside them, it is gone.
On the server. The platform records the full circle and flattens it centrally. Nothing is lost, but every flattened view costs server power.
In the browser. Each viewer's browser flattens the circle on screen. The full picture is recorded, every operator can look wherever they like, and the server does no extra work.
Our advice for most sites: record the full circle and dewarp on the server or in the browser, so the whole room is always there for investigation. Flattening only on the camera is the one choice you cannot undo.
A person near the rim of a fisheye picture appears rotated, compressed and seen from above, which is harder for any AI to read than an ordinary camera view. Detection is strongest near the centre and softer towards the edge.
Counting and occupancy near the centre of the circle work well. Identification tasks such as face recognition belong on entrance cameras, for the detail reasons above.
Whatever platform you choose, test detection across the whole circle, edge included, on your own footage. A demo filmed in the middle of the picture tells you little about the edge.
Coverage. Fisheye and multi sensor cameras cover 180 to 360 degrees all the time. A PTZ camera covers one direction at a time.
Detail at distance. Fisheye is lowest, falling towards the edge. Multi sensor is high in every direction. PTZ is very high, but only where it points.
Recording the whole scene. Fisheye and multi sensor cameras record everything in view. A PTZ camera records only where it was pointing.
Moving parts and cost. Fisheye and multi sensor cameras have no motors to wear out; PTZ cameras do. Fisheye is usually the most affordable of the three and multi sensor the most expensive.
Best fit. Fisheye for open rooms and overhead awareness. Multi sensor for large outdoor areas and perimeters. PTZ for following and zooming in on live events.
One warning applies to any mixed design. If a PTZ camera is zoomed in on one incident while another happens behind it, there is no footage of the second. A fisheye camera cannot miss it, even if it shows it in less detail. That is why strong designs use both: fisheye for continuous coverage, PTZ for close follow up.
Prices vary by resolution, build and brand. As a rough guide, consumer and small business fisheye cameras cost from under a hundred US dollars, while enterprise models with 9 to 12 megapixel sensors, good low light performance and vandal resistant housings usually cost several hundred to over a thousand dollars each.
The camera is only part of the bill. One fisheye often replaces two to four fixed cameras in an open room: fewer cable runs, fewer mounts and, on platforms that license per camera, fewer licences. On a platform with unlimited cameras on the licence, the choice comes down purely to coverage and detail.
Visylix is an automated AI video surveillance platform built in India. It watches every camera with AI, decides what matters, and acts on it. Fisheye cameras fit straight in.
The full circle, always recorded. Visylix records the original fisheye picture untouched, so the whole room is preserved for every investigation.
A virtual PTZ in the browser. Open any live fisheye camera and switch it into dewarp mode for a flat view with pan, tilt and zoom, from a tight 30 degrees out to a wide 150 degrees. The flattening happens on the operator's screen, so it adds no load on the server, however many people are watching.
Nothing cropped away. Grids, video walls of up to 36 tiles and playback show the whole circle, so the full room is always one glance away, and Visylix AI analytics run on the full original picture.
Licensing that rewards good design. Starter and Pro include unlimited cameras on the VMS licence, from ₹4,999 or $49 per month, so replacing four fixed cameras with one fisheye changes your coverage and cabling, not your licence bill. AI analytics are added per camera per month, on the cameras you choose.
Proven on your footage. If fisheye cameras are central to an analytics use case at your site, we test detection across the whole circle, edge included, during the proof of concept. And like everything in Visylix, it runs on your own hardware, including fully air gapped sites.
Fisheye cameras earn their place in open rooms where the question is "what happened here", such as retail floors, lobbies, open offices and waiting areas; where one camera can replace several, with fewer cables and mounts; where no blind spot beneath the camera matters; and wherever the whole scene must be recorded continuously, which no PTZ camera can do.
They disappoint when used to identify people at a distance; in long, narrow spaces where most of the circle covers walls; under very high ceilings; when only the camera flattens the picture and the original is discarded; and when analytics were tested at the centre and then relied on at the edge.
A fisheye camera is a fixed security camera with an ultra wide lens, usually 180 degrees, that captures a circular picture of everything around it. Mounted on a ceiling, one fisheye camera covers a full 360 degrees with no blind spot beneath it. Software then flattens the circle into normal looking views for operators.
Consumer and small business models start below a hundred US dollars. Enterprise models with 9 to 12 megapixel sensors, strong low light performance and vandal resistant housings usually cost from several hundred to over a thousand dollars. The real cost also depends on how many fixed cameras one fisheye replaces, and on how your video platform is licensed.
Dewarping is the software step that turns the curved fisheye circle into flat views that look like ordinary camera footage, such as a virtual PTZ view you can steer, an unrolled panorama or a four way split. It can run on the camera, on the server or in the viewer's browser. Running it on the server or in the browser keeps the full original picture for later investigation.
They do different jobs. A fisheye camera records the whole scene all the time, at moderate detail. A PTZ camera records only where it points, at high detail. For continuous coverage of an open room, choose fisheye. For zooming in on a live event, choose PTZ. Many well designed sites use both.
Usually only close to the point directly beneath it. Identification needs about 250 pixels per metre on the person under IEC 62676-4, and a fisheye camera spreads its pixels across a whole hemisphere. Use narrow view cameras at entrances for identification and fisheye cameras for awareness of the room.
Ceilings of about 2.7 to 4 metres work well. Much higher and people near the edge of the picture become very small. Much lower and the camera is easy to tamper with and mostly sees the tops of heads.
Yes. Visylix records the full original fisheye circle and lets operators open any live fisheye camera as a virtual PTZ view, with pan, tilt and zoom controls, right in the browser. Grids, the video wall and playback show the whole circle, so nothing in the room is ever cropped away, and AI analytics run on the full picture.