What is a Fisheye Camera? 360-degree IP camera, dewarping explained

What is a Fisheye Camera?

A fisheye camera uses a single high-resolution sensor behind a 360-degree hemispherical lens, capturing an entire room or area from one ceiling-mounted dome. The raw image is a circular fisheye distortion that the VMS or camera dewarps into one or more virtual flat views (panoramic strip, four-quadrant, or PTZ-style digital zoom). Common resolutions are 6MP, 12MP, and 16MP. Fisheye cameras replace three to four traditional cameras at indoor open-floor sites with one mount point and one cable run.

The short definition

A fisheye camera packs one large sensor (typically 1/1.7-inch or larger) behind a hemispherical lens that captures roughly 180 degrees in every direction. From a ceiling mount, that's the entire room below. The raw image is a circle inside a square frame with severe edge distortion; dewarping software corrects it mathematically into normal-looking flat views.

Top-tier fisheyes from Axis, Hanwha Vision, Hikvision (NDAA-blocked for federal work), Bosch, and Avigilon ship at 6MP, 12MP, and 16MP. The higher-resolution variants make dewarping practical: more raw pixels means each virtual camera still has usable resolution.

How dewarping actually works

Dewarping is a coordinate transformation. Each pixel in the output maps to a pixel in the raw fisheye source via a lens-specific projection function. Three modes cover most use cases:

Panoramic (180 or 360 degrees). Single horizontal strip showing the entire field of view. Useful for retail aisle ends, school corridors, and atriums.
Four-quadrant (quad). Four virtual flat cameras facing four directions, like four PTZs from one mount. Useful for office bullpens and open-plan rooms.
Virtual PTZ. One pannable, tiltable, zoomable view that the operator drives inside the captured 360. Live look uses a single virtual view; the full 360 is always recorded so historical PTZ is possible.

Dewarp can happen on the camera (saves VMS CPU; locks the dewarp mode at recording), in the VMS (more flexible; recording stays raw), or in the client viewer (most flexible, raw recording, slight client-side performance cost). Genetec, Milestone, Avigilon, and Verkada all support client-side fisheye dewarp on major brands.

Fisheye vs multi-sensor

Same coverage goal, different tradeoffs. Fisheye uses one sensor and one lens with software dewarp: lower hardware cost, but it loses pixels to the dewarp so per-face resolution drops at distance. Best indoors under 14-foot ceilings. Multi-sensor uses 3 or 4 sensors and lenses for true edge-to-edge resolution with no dewarp distortion, at typically 1.8 to 2.5x a fisheye from the same vendor. Best for outdoor corners, atriums, and high ceilings. See the multi-sensor entry.

Resolution and the per-face pixel question

Per-face pixel math separates a fisheye install that works from one that doesn't. Forensic capture typically requires 80 pixels between the subject's eyes. On a 12MP fisheye:

12MP fisheye, 12-foot ceiling. Subject at 8 feet from the mount: roughly 100 pixels between eyes. Forensic-grade.
12MP fisheye, 14-foot ceiling. Subject at 12 feet from the mount: roughly 70 pixels between eyes. Below forensic threshold; suitable for situational awareness only.
6MP fisheye. Halve those numbers. Use 6MP for indoor coverage where forensic capture isn't the goal.

For sites where the camera plan needs forensic capture at distance, scope multi-sensor or supplement the fisheye with a fixed bullet at the entry point.

Where fisheye is the right call

Open-plan offices. One 12MP fisheye covers a 1500 sq ft bullpen. Replaces four traditional cameras at one-third the cabling cost.
Retail mid-aisles. Center-aisle ceiling mount captures both sides of the aisle and the cross-aisle ends. Pairs well with vertical bullets at the registers.
Conference rooms and classrooms. One fisheye at the ceiling center covers all participants. Good for incident review and room utilization analytics.
Hospitality lobbies. Aesthetic dome form factor; one cable run; full 360 coverage. Pair with bullet at the entrance for face capture.

When to ask Tec-Tel about fisheye selection

Per-face pixel math is the part installers get wrong. We'll walk a building, mark up the ceiling plan, and tell you whether a 6MP, 12MP, or 16MP fisheye covers the zone or whether you need a multi-sensor instead. Free scoping call.

Frequent buyer questions

What's the difference between a fisheye and a multi-sensor camera?

Architecture. A fisheye uses one large sensor and one hemispherical lens, dewarped in software. A multi-sensor uses 3 or 4 separate sensors and lenses in one housing, each producing a normal flat image. Fisheye is cheaper and simpler but loses pixels to the dewarp. Multi-sensor delivers true edge-to-edge resolution at higher cost. Fisheye for retail and office, multi-sensor for forensic-grade outdoor and atrium coverage.

What does dewarping do?

Dewarping converts the raw fisheye image (a circular distortion of the scene) into one or more rectified rectangular views. Common dewarp modes: panoramic (a wide strip covering 180 or 360 degrees), four-quadrant (four PTZ-style virtual cameras inside one image), single-PTZ (digital zoom and pan inside the captured 360 view). Dewarp can run on-camera, in the VMS, or in the client viewer.

Where should I mount a fisheye?

Center of an open ceiling, typically 8 to 14 feet high. The camera covers everything below it within a roughly equal radius (12 to 14 feet at typical mount heights). Don't wall-mount unless you specifically want a 180-degree wall view; ceiling-center delivers the design intent. For high ceilings (warehouse, atrium) over 20 feet, expect noticeable resolution loss at floor level and consider a multi-sensor instead.

How many pixels does a fisheye actually deliver per face?

A 12MP fisheye captures roughly 4000 by 3000 pixels in a circular area. Dewarped, that's about 700 pixels horizontal across each quadrant of a four-PTZ view. Face-readable capture (typically 80 pixels between eyes) works to about 12 feet at that resolution. Beyond 12 feet, the per-face pixel count drops below the forensic threshold. That's the practical range.

When should I avoid a fisheye?

Three scenarios. (1) High-ceiling installs where the floor is more than 14 feet from the camera. (2) Forensic-grade requirements like court evidence at long range. (3) Sites with poor lighting; fisheye sensors split light across a hemispheric lens, which costs low-light performance compared to a fixed-lens camera. For those, use multiple traditional cameras or a multi-sensor.

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What is a Fisheye Camera?

The short definition

How dewarping actually works

Fisheye vs multi-sensor

Resolution and the per-face pixel question

Where fisheye is the right call

When to ask Tec-Tel about fisheye selection

Frequent buyer questions

Multi-sensor camera

Dome camera

WDR (Wide Dynamic Range)

Industries

Start with a free consultation.

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