Functions; Gain; Shutter; Absolute Value Control For The Shutter - Sony SX90 Technical Manual

Functions

Gain

Both Manual and Auto Gain settings are available with
this camera.
The variable range extends from 0 to 24 dB for the black
and white models or from 0 to 18 dB for the color
models. The camera is designed so that the gain can be
subdivided and set by 0.0359 dB.
At the factory default setting, the gain is set to 0 dB.
When Auto Gain is selected, the gain is adjusted
automatically, based on the brightness of the subject. At
this time, the reference level (target point) is set in the
AutoExposure register.
For details on AutoExposure, see "Auto Exposure" on
page 10.

Shutter

This camera allows both Manual and Auto Shutter
settings.
The variable range extends from 10 microseconds to
16.0 seconds; relative values are indicated by a 12-bit
integer, and absolute values are indicated using a 32-bit
floating point value.
The relationship between the parameter and the
exposure time is given by the following formulas,
where:
P = Parameter (003h to 47Eh)
E = Exposure time (s)
If P= 3
E = 0.00001
If 4 <= P <= 1000
If 1000 <= P <= 1150
Setting examples
3 (003h) : 10 µs (1/100000)
32 (020h) : 1 ms (1/1000)
100 (064h) : 10 ms (1/100)
1000 (3E8h) : 1 s
1010 (3F2h) : 2 s
1150 (47Eh) : 16 s
1
16 s
1 s
1
10 µs
3
When Auto Shutter is selected, the exposure time is
adjusted automatically, based on the brightness of the
subject. At this time, the reference level (target point) is
set in the AutoExposure register.
For details on AutoExposure, see "Auto Exposure" on
page 10.
For long exposure times
When the exposure time is longer than the frame period,
the camera enters the long exposure time mode, and the
actual frame rate is reduced in accordance with the
exposure time.
Absolute Value Control
for the Shutter
This camera allows control of exposure time using
absolute values. The values are indicated using a 32-bit
floating point value. (Unit: sec.)
The variable range of absolute values extends from 10
microseconds to 16.0 seconds.
Programming example
union
{
DWORD dwValue; // 1394 is expressed in quadlets,
float fValue; // exposure time is indicated in seconds.
} AbsoluteShutterValue;
AbsoluteShutterValue.fValue = Exposure time;
WriteQuad(AbsoluteShutterOffsetAddress,
AbsoluteShutterValue.dwValue);
WriteQuad is a virtual function used to write in the 1394
register.
AbsoluteShutterOffsetAddress is an offset address for
the absolute value control.
See "ConfigurationROM" on page 18 for the formula
for the offset address.
2
1000 1150
9