12
13
Adjustment of flange
focus for variable
focus lenses
To obtain a sharp definition, point the camera at an object which is at least 5 times the
minimum lens distance (MOD) of the lens. (If this is 1m, the object must be at least 5m
distant from the camera).
Open the iris fully and set the lens to the maximum tele position and focus with the focus
ring.
If the lens has automatic iris control, select a dark object (or use an ND filter, 64-x)
to ensure that the iris is fully open.
Set the lens to the maximum wide-angle position.
Undo set screw
M
and turn the C/CS ring on the camera until an optimal sharpness is
reached. Repeat the process for checking purposes, if necessary.
When finished, retighten screw
M
.
Note
The value stated in the diagram as
AL
(depth of thread of the lens with CS mount:
<- 5mm) must be observed. The camera may be damaged if this value is exceeded.
When installing a lens with CS mount, never use the C-mount adapter ring.
Addition when using
cameras for day/
night application
Even if the lens is IR corrected (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.
Explanation of terms for iris setting
AGC (automatic gain
control)
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 0.8 and 1.0Vp-p.
White clip
Signal limitation at high image amplitudes. The white clip value generally lies between
1.1 and 1.2 Vp-p.
AES (automatic
shutter control)
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).
Iris adjustment
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).
Содержание ENC-501L
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