Eneo VKC-1340/IR Mode D'emploi page 41

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Addition when using
lenses for
day/night application
Explanation of terms for iris setting
AGC (automatic
gain control)
White clip
AES (automatic
shutter control)
Iris adjustment
IR cut filter
Important note
on the IR cut filter
Even if the lens is a day/night lens with stabilised focus regulation 0-focus shift), a
minor flange focus is possible between visible light and IR light.
If there is a day/night application with IR illumination, the flange focus should be set
under IR light conditions. This is because the iris is generally opened when used at
night due to the poor level of light and low depth of focus. During the day, the iris is
continuously closed further, there is a greater depth of focus and the difference in the
flange focus is compensated.
This starts tooperate when the light intensity is insufficient to deliver a full video signal
(1Vp-p). The greater the gain, the greater the signal noise in the picture.
It is generally activated between 0.8Vp-p and 1.0Vp-p.
Signal limitation at high image amplitudes.
The white clip value generally lies between 1.1Vp-p and 1.2Vp-p.
This automatically controls the shutter times, it starts when the light intensity becomes
stronger and the signal would otherwise be limited/over-regulated by the white clip
feature. Automatic shutter control is mainly applied for manual lenses.
If a camera is operated with controlled lenses, regardless of whether DC or AI, the AES
must be switched off. Problems arise if this is not done because both control systems
try to steer the volume of light for the camera. As the AES generally reacts faster, the
iris remains fully opened and the shutter resumes the control work, which produces
major drawbacks. As the iris is open, the depth of focus is very low. When shutter times
are short, this can cause a smear effect (bright, vertical stripes in light parts of the
picture).
The working point of the iris should always be above the AGC start and below that of
the white clip. This range is very small with some cameras, making it difficult to adjust
the lens. It is therefore advisable to switch off the AGC (if possible) when adjusting the
iris. Once the lens has been focussed, the AGC must be switched back on (only for
cameras which allow the AGC to be switched off).
In the case of DC lenses, the working point of the iris is adjusted at the camera's level
potentiometer (the AI amplifier is built into the camera).
In the case of AI lenses, the level potentiometer is located on the lens (the AI amplifier
is built into the lens).
If an IR light source is used for illumination and if this exceeds a certain brightness,
the filter is panned in. The brightness can then no longer be sufficient and the filter is
panned out. This can lead to the filter being constantly panned in and out (with a time
delay) in a special configuration. This can be prevented by
a) reducing the light level
b) toning down reflectors
c) changing the image
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