Measuring maximum scene illumination for a camera

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Measuring maximum scene illumination for a camera

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Measuring maximum scene illumination for a camera

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There is a camera. It is required to measure maximum scene illumination, at which this camera produces image without brightness limitation.





Luxmeter (a device for measuring illumination). Almost any kind of such a device with standard CIE spectral response will suit.
Projector with tungsten halogen lamp 220V, 1000W or more.


Such projector can create illumination up to 150000lx, what exceeds illumination in bright sunny day on mid-latitudes (100000-120000lx).


Work carefully with the projector. There is danger of overheating and inflammation of fire hazardous materials next to the projector.


Lens with F1.2 aperture, parameters of which are reliable, focal length is 4-8mm.


If the camera allows to mount only mini-lenses (M12), the mini-lens with a known aperture (F2.0) is needed.


A sheet of crumpled white paper.


Stand. It is recommended for convenience and accuracy.



Order of work


1. Switch off all additional options of image processing. Only AESC and AGC should be switched on.


2. Mount lens F1.2, on the camera, mount the camera on stand, direct it towards sheet of paper, connect to computer, display image on the screen.


If the camera allows mounting only mini-lenses (M12), mount a mini-lens with known aperture (F2.0).


3. Reduce contrast of the monitor to 50-70% of maximum.


4. Close to the sensor window directly on the sensor, fix a small piece of crumpled white paper.


5. Switch ON the projector.


6. By changing the distance from the projector to the luxmeter sensor, obtain the image on the screen with a little bleeding whites on the bends of the rumpled sheet of paper.


You must not change the lamp supply voltage. It should be equal to nominal lamp supply voltage. Change Illumination only be means of distance variation between the lamp and the sheet of paper.

Be sure, that the luxmeter sensor window and the small piece of paper on the sensor have visually equal illumination.


7. Record the maximum illumination according to the luxmeter reading.


Maximum illumination for black/white cameras with 1/3" CCD image sensor with exposure range of the electronic shutter up to 1/100000s and lens with the aperture F1.2 make approximately 20000..30000lx. It allows using these cameras indoor with any lenses or outdoor with auto iris lenses or lenses with maximal aperture no more than F2.5.

Maximum illumination for high-quality color cameras or day/night cameras exceeds 100000lx. For mini-cameras with image sensor format of 1/4" the maximum illumination can be considerably lower.


As in cameras' specification there is no the Maximum illumination parameter, in VideoCAD the maximum illumination is not specified separately and is calculated inside the program. For accurate modeling maximum illumination, first specify all other camera parameters and then choose the Maximum signal/noise ratio for obtaining a little bleeding whites at the measured maximum illumination.