Af (Auto Focus) Control - JVC GR-DVA10 Technical Manual

2.3.2 AF (Auto Focus) control

1. Auto Focus operation during slow shutter mode
Though the basic Auto Focus operation is the same as usual, the interval of Auto Focus operation varies
conforming to the timing of the picture data renewal when the camera is in the slow shutter mode. For
example, in case the Gain-up mode is set to Auto, the shutter speed is changed to 1/30(2V) according to
the illumination of the object. Therefore, the Auto Focus operation also works every 2V. The Auto focus
operation works every 4V in Slow-4X mode and every 10V in Slow-10X in the same way.
V D
Data
Renewal/processing
Focus
operation
2. Improvement of the Low-contrast performance
To improve the AF performance in the low contrast subject (such as the man's face), a route that has low
stage filter (HPF1) is added newly. The low contrast subject contains the frequency element that is not
comparatively high.
Previous
N e w
Fig. 2-3-6 AF operation timing in slow shutter mode
B P F H P F 2
H P F 1
H P F 2
H P F 1
B P F
H P F 2
H P F 1
H P F 2
Fig. 2-3-7 Addition of AFE low stage filter
1/30
1/60
2 V
P e a k
Rectifier
Addition
P e a k
Rectifier
Addition
P e a k
Rectifier
Addition
P e a k
Rectifier
Addition
P e a k
Rectifier
Addition
P e a k
Rectifier
Addition
P e a k
Rectifier
Addition
2-13
A F E
H P E
H P F 1
H P F 2
A F E 1
H P E 1
A F E 2
H P E 2
H P F 1
HPF1: 500KHz
HPF2: 1.7MHz
H P F 2