PTZ Versus Fixed MP Camera Shootout

Benros Emata

•Published Apr 30, 2011 04:00 AM

As megapixel surveillance cameras become mainstream, many have begun questioning the value of PTZs. The main criticism of PTZs is that they can only provide good image quality by 'looking' at a very small area at any given time. Megapixel cameras, on the other hand, can see 'everywhere' at all times. With their significantly increased resolution, operators can simply digitally zoom to magnify any area of interest. With this approach, the megapixel camera provides the best of both worlds - capturing details at a distance while recording video across large areas.

But how true is this really? What drawbacks does a MP camera have compared to a PTZ and in what scenarios?

In this report, we share our test results of a shootout between a PTZ camera and 4 megapixel cameras (ranging from 720p to 5MP from Axis, IQinVision, Sony and StarDot). We wanted to see what tradeoffs would be revealed if we tested these cameras at the same time and in the same space.

We took our 5 camera test rig and set up at a moderately sized public parking lot. See the test location below:

We then set up a series of tests (during the day, twilight and nighttime) where a subject would move across the covered area. We tracked the subject with our PTZ camera and then contrasted the PTZ's resulting image with that of the megapixel cameras. The overview image below shows the dimensions of the test area and the key testing points we selected:

We then conducted competitive analysis for various scenes to rate and compare the relative performance of each camera. Here are the 15 scenarios we analyzed:

PTZ Capture Area vs MP Capture Area
Daytime Comparison by Distance / HFoV - 5MP vs PTZ
Nighttime Comparison by Distance / HFoV - 5MP vs PTZ
Midday Even Lighting (Far Subject)
Midday Even Lighting (Mid Subject)
Midday Even Lighting (Near Subject)
Twilight Harsh Lighting (Far Subject)
Twilight Harsh Lighting (Mid Subject)
Twilight Harsh Lighting (Near Subject)
Nighttime Lighting (Far Subject)
Nighttime Lighting (Mid Subject)
Nighttime Lighting (Near Subject)
Daytime License Plate Capture (Far Subject)
Daytime License Plate Capture (Near Subject)
Nighttime License Plate Capture

We found the results, and especially the tradeoffs, to be fascinating.

Megapixel cameras do not provide anywhere close to the level of range and detail that an operator controlled PTZ can provide. It is simply no contest. Claims to the contrary are little more than marketing hype. The level of disparity is dramatic. While the move from SD to MP has improved fixed camera coverage range, it is still nowhere close to what PTZs can provide. For instance, while the PTZ captured facial details at over 250 feet from the camera, the megapixel cameras struggled to capture even 30 feet. This disparity occurred even though we used a relatively narrow Fov (~50 Degrees) for the megapixel cameras. The relative results would have been far worse compared to a MP wide angle lens or a 360 degree camera (see our Theia wide angle test results and our Mobotix 360 test results for a comparison).

From our test results, here are our best cases for using megapixel vs PTZ:

The area to be covered is fairly small - say 300 square feet (or 30 square meters). This is tiny for outdoor areas but could be feasible in a small parking lot, entranceway, back alley, etc. In such areas, the MP can provide similar level of details for security purposes but with the added benefit of covering the whole area at all times.
The area to be covered is moderately sized - say a few thousand square feet (or a few hundred square meters) and you can accept getting mostly blurry images of people, cars and plates. The plus side is that the MP camera will provide relatively low quality images while the PTZ will provide nothing unless it happens to be pointed at a specific area where an incident is occurring.
You do not plan to have an operator monitor / control the PTZ. This case is a general argument for using fixed cameras over PTZs. Megapixel simply makes the fixed camera moderately better.

The video below overviews our key findings in a compact 10 minute video:

PTZ vs MP Capture Area

The image below provides a visual representation of the massive disparity between the PTZ's potential coverage area and the MP camera's actual coverage area achieved in the test. We defined coverage area as the geographical zone that the cameras can provide facial or license plate details.

Day Comparison By Distance / HFoV (5MP vs. PTZ)

The image below should help you understand the tradeoff between the two camera categories across a large area. Notice how the megapixel camera's image quality degrades substantially as the FoV widens but that the PTZ, using its optical zoom, can continue to provide a relatively detailed image. Remember, this comparison presumes the PTZ is actively tracking a subject.

Night Comparison By Distance / HFoV (5MP vs PTZ)

The image below shows the same contrast with the same fundamental tradeoffs, now at night:

Midday Even Lighting (Far Subject)

In this scenario, the MP cameras are digitally zoomed into our human subject ~275ft out where the horizontal FoV (HFoV) is ~256ft. The PTZ is maximally zoomed into the same human subject. The PTZ's HFoV at this distance is ~7.3ft. Note that the scene is slightly backlit due to the relative position of the light source or sun.