Exposure Time and Long Time Exposure

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Exposure Time and Long Time Exposure


Exposure Control Features


The exposure time is not a mandatory GenICam feature. Nodenames for the camera exposure time might also be different between model from different manufacturers.

The number of acquirable images of course depends on how long each single frame is going to be exposed.

As long as the Acquisition Frame Rate value is on its maximum, the camera will try to acquire as much frames as possible.

The upper limit of possible frames is however set by the exposure time.

Exposure time can be directly set as a duration in µs.

Increasing the exposure time reduces the acquisition frame rate and vice versa!


ExposureMode = Timed / TriggerWith / TriggerControlled

Timed       : exposure with defined duration (ExposureTime), start with FrameStart or LineStart


TriggerWith : exposure time defined by frame or line trigger signal width. 
  RisingEdge or LevelHigh -> exposure duration equals trigger HIGH,

  FallingEdge or LevelLow  -> exposure duration equals trigger LOW


TriggerControlled : exposure duration based on one or more trigger signals


ExposureTime   = <value>us 



ExposureTime         ExposureTime1


Exposure time in CVB

The CV Gen API itself provides no dedicated function to dynamically set the Exposure Time directly.

Please implement Exposure Time settings as described in the Common Vision Box Manual in the chapter Image Manager - GenICam Library.


Setting Long Time Exposure (LTE)


As the values for standard exposure times (in us) are too low for LTE applications, the exposure time can be set with Pulse Width Control.

Shutter mode will be invalidated automatically when using Pulse Width Control.

Acquisition and Trigger Control:

First, the Exposure Mode has to be be set to "Pulse Width Control", because the values for standard exposure times (in us) are too low for LTE applications.

This automatically invalidates the Shutter Mode, i.e. its configuration has no influence on image acquisition anymore.


Digital I/O:

To set the correct signal routing, one of the freely programmable signal lines (Line Source) has to be selected, in this case "Pulse Generator 0".


Pulse Generators:

To configure the signal itself with the duration of exposure, its Start Point, Length and End Point can be modified according to individual timing requirements.

With a Pixel Clock of 60 MHz the exposure time is about 300 ms in example below.

The computation of the exposure time can be found in the camera's manual in chapter "Pulse generators".

To run Pulse Width Control with Software Trigger the settings are as follows:


Exposure Mode

: Pulse-width control

Line Selector

: Pulse Generator 0

Line Source

: Software Trigger 0

Pulse Generator Selector

: Pulse Generator 0

Clear Mode for the Pulse

: High / Low Level | Rising / Falling Edge