Determining a Camera’s Low Illumination Performance

3 Examples Highlight How It Works

Let’s run some more calculations to see how this works out.

Example One: Let’s check the following parameter in black/white mode –

In this example, the F-stop value of Camera B is greater than Camera A. Therefore, the amount of light available in Camera B is less than Camera A in the same conditions. If the amount of light gathered by Camera B were to be set the same as that of Camera A, the video amplitude of Camera B’s output signal will be larger. In this example, as it reaches 40 IRE, the low illumination performance of Camera B will be indicated as [email protected] (40 IRE AGC “on”). If the amplitude of Camera B is kept at 30 IRE, then the illumination required by Camera B to produce the signal will be less than 0.1 LUX. If camera B only requires 0.05 LUX to produce
this signal, the low illumination performance of Camera B will be equivalent to [email protected] (30 IRE AGC “on”). Thus, the low illumination performance of Camera B is better than Camera A.

Example 2:

Note that all parameters are the same except that the IRE value of Camera B is greater. In other words, the video amplitude of Camera B (350 mV) surpasses that of Camera A (210 mV). Therefore, the illumination required by Camera B to produce the same signal amplitude as Camera A will be less than 0.1 LUX.  If Camera B only requires 0.05 LUX, the low illumination performance of Camera B will be equivalent to [email protected] (30 IRE AGC “on”), confirming that the low illumination performance of Camera B is superior.

Example 3:

In this example, everything is the same except that Camera A produces a video amplitude of 210 mV when AGC is “on” while Camera B produces the same amplitude if AGC is “off.” So, let’s infer that the signal amplitude of Camera B will increase if AGC is “on.” If it reaches 50 IRE (350 mV) with the AGC “on”, the environment illumination required by Camera B to produce a signal of 210 mV amplitude will be less than 0.1 LUX. If it is 0.05 LUX, the low illumination of Camera B will be equivalent to [email protected] (30 IRE AGC “on”). Therefore, the low illumination performance of Camera B is better than that of Camera A.

As you use this tool for measuring a camera’s low illumination, be sure that you use an identical environmental illumination for the different cameras. Employ the same lenses with identical focal lengths to shoot the same object in the same conditions. Also, set the AGC function to the same level. Then, the brighter the video, the better the low illumination.

Mark S. Wilson is Vice President of Marketing for Infinova.

 

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