Exposure End Event on ace and ace 2 Rolling Shutter Cameras#
ace Cameras#
On ace rolling shutter cameras (e.g. acA4024-8gm), the Exposure End event always takes place at the end of the readout of the first sensor row, regardless of the actual ROI setting. The event notification is being sent out immediately at this point. The event contains the frame ID as well as a timestamp.
Note that on rolling shutter sensors, there is a time difference between exposure end of row 1 and exposure end of row N as described here.
If you need to know the "real" end of exposure of the image ROI, Basler recommends taking the Exposure End event timestamp as the starting point and calculating the remaining exposure time with tRow (e.g. 35µs for the acA4024-8gm):
tRow x (image ROI OffsetY + image ROI Height -1)
You can determine the tRow value for your camera model from this list.
However, if you are using the GRR (Global Reset Release) sensor readout mode with flash lighting or a flash window in rolling shutter mode, calculating this is probably not necessary, since the "effective" exposure time for the flash window ends with the start of the readout of the first row.
If the camera is configured for free run image acquisition and the shutter mode is set to Rolling, the camera automatically is in overlapping image acquisition mode. In that case, depending on other parameters, the camera might start with a new frame / exposure of row 1, even if the exposure of the previous frame is not yet finished. See here.
ace 2 Cameras#
The Exposure End event behavior has changed with ace 2. On ace 2 cameras, the Exposure Start and Exposure End events are derived from common Exposure Active signals. Note the plural here because the Exposure Active signals of successive frames can overlap. Therefore, the Exposure Start event of a frame may occur before the Exposure End event of the previous frame.