Extended shutter mode operation for IIDC-compliant Imaging Products

Last Revision Date: 1/30/2015

Most of our IIDC-compliant imaging products have extended shutter functionality for increasing the maximum integration time to several seconds or more.

Extended shutter capability is controlled using the FRAME_RATE register 0x83C. Access this register using the FlyCap demo program included with the latest version of the FlyCapture SDK. In FlyCap, Frame Rate graphical controls are found under the General Camera Properties tab of the Camera Control dialog.

Extended Shutter and Frame Rate Interaction:
When the FRAME_RATE is in AUTO mode and is ON, the actual rate of image transfer is determined by the CURRENT_FRAME_RATE register 0x600.

When the FRAME_RATE is in MANUAL mode and is ON, the Frame Rate value determines the rate of image transfer and the maximum rate at which the shutter closes.

The shutter must close before the image/frame is transferred off of the camera. When the FRAME_RATE is OFF, extended shutter times are possible because the actual frame interval is no longer fixed. The reason for this is that the Frame Rate value only determines the rate of transfer when the shutter value (i.e., integration time) is less than the frame period. This also affects the amount of bandwidth that is required by the camera (i.e., low frame rate = low bandwidth).

If the shutter integration time is longer than the Frame Rate period, then the shutter will control the perceived Frame Rate, since it is no longer possible to provide the same Frame Rate while having an increased shutter time. This is why the frame rate displayed in the FlyCap status bar may be less than the value specified in the “Format and Frame Rate” control dialog.

Please consult the Register Reference, available in our Downloads section, for more information regarding the FRAME_RATE and CURRENT_FRAME_RATE registers.