Shutter (Exposure Time)

Supported by ...

All Pixelink Cameras

Description

The shutter feature controls the exposure time of the sensor. Increasing the shutter integration time makes the image brighter. On CMOS sensors, increasing the shutter integration time will also increase the amount of noise in the image.

The shutter can be controlled manually, once automatically or fully automatically (also referred to as continuous auto exposure). In the auto modes, the camera will attempt to set the shutter feature such that a small portion of the scene is saturated. The continuous auto exposure mode is especially suited and useful in microscopy applications, such as pathology, where frequent microscope objective changes occur. It has been designed for this environment and works very well. However, there is an assumption in the algorithm that the scene is back-lit and that part of this bright light is visible to the camera as white. In situations where the scene is uniform grey, the camera will try to make a portion of the scene saturated which may result in overexposed images. In such cases, the auto exposure functions should not be used.

Please note: For some older FireWire cameras, when the Frame Rate control is active (ON), the Shutter control is limited by the Frame Rate control setting. For example, if the Frame Rate control is set to 50 fps, the maximum value of the Shutter control will be limited to 20 ms. For unlimited control of the Shutter feature, the Frame Rate control must be turned off.

The shutter operates in a number of different modes that determine the speed of the readout and the ability to capture stop motion. The available shutter modes, described below, are determined by the type of sensor in the camera. They are controlled by the Trigger Feature.  

• In global shutter mode, the Shutter control determines the length of time from the frame reset to the start of readout. Readout and exposure occur sequentially. The sensor has limited to no sensitivity during the readout phase.

• In rolling shutter mode, the Shutter control determines the number of lines in the ROI that are active at any time. Readout and exposure occur concurrently.

• In Fast Reset Shutter mode, the Shutter control determines the length of time from the completion of frame reset to the start of readout. Readout and exposure occur sequentially. The sensor remains sensitive during the readout phase so controlled lighting or a mechanical shutter may be required.

API Control

PxLGetFeature, PxLSetFeature

Note: FEATURE_SHUTTER and FEATURE_EXPOSURE are equivalent.

A set operation (PxLSetFeature on FEATURE_EXPOSURE) can take 1 parameter, or if the FEATURE_FLAG_AUTO, or FEATURE_FLAG_ONEPUSH flag is used to initiate an auto operation, an additional two parameters can be specified. Similar to FEATURE_FOCUS, these two (optional) additional parameters represent a lower limit, and an upper limit (in that order), to be used when performing the auto operation. In this specific circumstance, the first parameter will be ignored.

Performing a get operation (PxLGetFeature on FEATURE_EXPOSURE) while specifying 3 parameters, will return not only the current exposure value (the first parameter), but also the limits that will be used for an auto set operations (the 2^nd and 3rd parameters).

Use PxLGetCameraFeatures for FEATURE_SHUTTER to determine if a particular camera supports user-defined limits for the auto operation.

Feature Flags

Parameters 

PL-X Cameras:

PL-D Cameras:

* FFR Mode is available on PL-D cameras using Sony IMX sensors, and can be used to obtain higher frame rates than can be otherwise achieved in the camera's normal mode of operation. For more information, see: Special Operation Mode

PL-B Cameras: