Does the selection of a smaller area (e.g. with binning, ROI) improve the read out time and the imaging frequency?
Vertical reduction of the exposed area (e.g. by binning) reduces CCD read out time. Setting an ROI (region of interest) has the same effect. The read out time for the non-exposed lines (skipped lines) is scaled down by a factor of 4. Reading out a VGA line takes 64 µs, where reading out a SuperVGA line takes 117 µs. Horizontal binning or horizontal ROI does not affect the read out time. Example: For a VGA 640×480 sensor, a ROI of 400(H)x200(V) is selected. At full resolution, the read out time would be 32 ms. The ROI reduces this time. The resulting actual read out time is displayed in the info window. Calculation: 200 lines are read out with 64 µs per line. This gives 12.8 ms. The remaining 480 – 200 = 280 lines which have not been exposed (skipped) are read out at quadruple speed, thus 280 : 4 = 70, 70 x 64 microseconds = 4.48 ms. Summing up we obtain a read out time of 12.82 ms + 4.48 ms = 17.3 ms. The imaging frequency is therefore 57.8 Hz.
