Avigilon Real Time Exposure And Gain

By Derek Ward, Published Feb 24, 2015, 12:00am EST

Knowing how exposure and gain impact image quality, bandwidth, and camera performance can useful in installation and troubleshooting.

Very few cameras readily expose this information, making it difficult or impossible to find for most users.

However, Avigilon includes this information right in the web interface of their cameras, updated in real time.

In this note, we share videos of this feature in action, showing how exposure and gain vary across WDR and adaptive IR scenes.

Real Time Exposure and Gain Display

Gain and exposure are displayed in the admin section of the camera's web interface, under the "Image and Display" section. They are displayed in real time, right next to the zoom and focus controls, seen here in this video demonstration:

Potential Uses

Knowing current exposure and gain is useful in a few ways, both educational and practical:

  • Low light impact: First and foremost, users may see in realtime how exposure and gain increase as light is lowered. These settings impact bandwidth and image quality greatly, and understanding how they work is key.
  • IR impact: Watching these settings, users may see the impact of built in IR, as exposure and gain remain relatively low compared to IR off. Additionally, we can check whether "adaptive IR" is simply adjusting exposure, or IR power, depending on which remains constant when subjects are enter the scene.
  • WDR: In real time, the difference in exposure time between a single exposure and multiple exposures used for WDR may be checked. This may also be used to view WDR's impact on exposure at night, in cameras which do not turn off WDR.
  • Troubleshooting: Occasionally, cameras may become noisy, dim, or blurred seemingly for no reason. Checking exposure and gain may assist in troubleshooting, as higher gain and exposure in full light may indicate a shutter or processing problem.

Users should see our Gain / AGC Impact and Shutter Speed / Exposure reports for more information on these two settings and how they impact image quality.

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Feature in Action

First, we lowered lights from 160 lux to about .1 lux with IR off to see how the camera adjusted exposure and gain. Exposure doubles when lowering lights from ~160 to ~110 lux (8.3-16.6ms), and again when moving from ~110 to ~1 lux (16.6 to 33.2ms). At ~1 lux, and below, the camera is using its maximum exposure, 33.2ms. Gain increases steadily as lights are lowered, from 3.8 to 28 dB.

True WDR Exposure Time

Comparing readings with WDR On vs. WDR Off, we can see that exposure is reduced by half, due to the reduction from multiple exposures (in a true WDR camera) to a single exposure. Note that gain remains fairly stable.

Adaptive IR

Finally, we take a look at Avigilon's Adaptive IR Setting (sometimes called smart or intelligent IR). By measuring IR illumination at this point, we can confirm whether IR power being reduced, the camera is adjusting exposure and gain, or all of the above, to avoid overexposure.

With our subject stationary in the field of view, we measured IR power, finding only a marginal difference in IR power between adaptive IR on or off. However, gain is lowered when adaptive IR is on, 12.8 vs. 18.8 dB.

We then zoomed the camera in to see how IR power increased, and its impact on exposure and gain. IR power is again only slightly different with adaptive IR on vs. off. However, with the subject moving through the field of view, we can see gain decrease from ~18 dB to 11.3, seen below with adaptive IR on. With adaptive IR off, it decreases much less aggressively, from ~19 dB to 17.3, only a 2 dB difference. 

Because IR power remains similar, we can determine here that Avigilon's main strategy for reducing overexposure in this scene is more aggressive gain reduction.

Other Manufacturers

Few, if any, manufacturers other than Avigilon offer the option to monitor these camera parameters in real time, despite some competitors (notably Axis and Mobotix) displaying many low level details in overlays, exposure and gain remain rare.

Members, if you know of others, leave them in the comments!

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