JVC KY-F58 Instruction page 27

TECHNICAL INFORMATION (Cont'd)
Operations Principles of the Electronic Shutter
(with the 1/500 sec. setting)
Electric charge is stored in the CCD image sensing device only
for a 1/500 sec. before the signal is read from the CCD image
sensing device. At this time the electric charge stored previ-
ously is discharged to another electrode. This process enables
shutter operations with 1/500 sec.
Vertical blanking period
Vertical sync.
signal
CCD device Signal discharging timing
signal reading
timing
Unnecessary
charge
CCD electric
charge
storage
Electric charge
to be stored
Video output
● Caution for electric shutter mode
• On a monitor, the movement of the object looks like the ones
taken under a strobe shot because an image of 1/500 sec. is
detected every 1/60 sec. [U Ver.] or 1/50 sec. [E Ver.] .
• Flicker occurs under a light such as fluorescent lamp which
lights cyclically. Adopting a light like an incandescent lamp
which lights constantly is therefore necessary.
• With the 1/500 sec. shutter mode, the storage time of the
CCD image device is approx. 1/8 [U Ver.] or 1/10 [E Ver.] of
that of normal the mode, and also the sensitivity is 1/8 [U
Ver.] or 1/10 [E Ver.] of that of the normal mode. This causes
a shortage of light, so that it is recommended to increase
the light volume by increasing the illumination to 800% [U
Ver.] or 1000% [E Ver.] or opening the lens iris about 3 steps.
ALC and EEI Operations
ALC stands for automatic level control, and EEI means shutter iris
control. With FULL AUTO mode, it adopts a system for maintaining
a certain level of video by combining the lens auto iris, the continu-
ous variable electronic shutter (EEI) and the automatic sensitivity
adjustment circuit (ALC).
The automatic sensitivity adjustment circuit works under low illumi-
nance, and the electronic shutter works under high illuminance.
Moreover, when the iris is set to AUTO, sensitivity, the iris and the
electronic shutter change continuously to acquire the appropriate
signal level automatically at any time.
In the ALC mode, there is sensitivity from 0 dB to +18 dB under low
illuminance. In the EEI mode, the electronic shutter varies the shutter
speed automatically from 1/60 [U Ver.] or 1/50 [E Ver.] to 1/1920 [U
Ver.] or 1/1600 [E Ver.] sec. The signal level is adjusted in the range
of 3 ( dark) to 5 ( bright).
When the iris is set to the manual mode, the sensitivity and the
electronic shutter vary continuously without varying the iris setting.
This function enables recording an object without varying its depth
under variable illuminance.
Illuminance: lx
8 16 32 62.5
With a lens ALC
+18dB +12dB +6dB
Without a lens
Signal reading timing
1/500 sec. 1/60 sec.[U Ver.]
1/50 sec.[E Ver.]
Effective charge
This is the calculated value, which is different from the actual
value displayed on the screen.
125 250 500 1000 2000
F1.4 F2 F2.8 F4 F5.6
F1.4
ALC
+18dB +12dB +6dB
SLOW SHUT Function
This function is used to record an object brighter than it ap-
pears in a dark place.
This function adopts a system which acquires higher electric
charge by taking a longer time for storing electric charge into
the CCD image device, not that the system increases GAIN
electrically. This enables the recording of an image with high
sensitivity even under conditions of less light.
The max. storage time is approx. 8 sec. (240 frames [U Ver.]
or 200 frames [E Ver.] ). One frame image is output for several
frames, therefore, the video output signals are latched into a
memory by using a WEN signal which is output at the same
time. On a monitor, the movement of the object looks like the
ones taken under a strobe shot
● When the SLOW SHUT is set to 3FRM
CCD storage
electric charge
Video output
signal
WEN output
signal
Note:
• With the AUTO IRIS MODE, the normal video level can-
not be used. Set to the MANUAL IRIS MODE and adjust
the diaphragm of the iris.
• By switching the HI-RESO mode, the FIELD OUTPUT
and FLAME OUTPUT can be selected.
• When the flame number is increased, noise may also
increase. Set it to the appropriate value.
4000 8000 16000 32000
EEI
1/120[U Ver.] 1/240
1/100[E Ver.]
F8 F11
F16
EEI
1/120[U Ver.] 1/240 1/480 1/960 1/1920[U Ver.]
1/100[E Ver.] 1/1600[E Ver.]
7. OTHERS (Cont'd)
64000 128000 256000
1/480 1/960 1/1920[U Ver.]
1/1600[E Ver.]
Revised in August 1998 27