Limited running time

[li779]

In my program, picamera takes 20s to take a picture with exposure value of 6s. Any suggestions on why this happens and how we can improve the running time?
The camera I am using is in V1 mode and other parameters are following:
brightness 50
analog gain 1
color effect None
crop (0.0, 0.0, 1.0, 1.0)
digital gain 17/16
drc strength off
exposure compensation 0
denoising False
meter mode average
saturation 0
sharpness 0

[6by9]

This has been covered multiple times in the forums.

Any frame that is requested will be completed. On changing mode/starting the sensor the first frames after the switch is always dropped as it is incorrectly exposed.

With the normal mode of operation a preview frame is requested, first frame is dropped, second frame is captured to generate the preview frame, then the sensor changes mode for the capture, drops the next frame, and captures the second one. If the exposure time is 6 seconds, then each frame takes that long, and I'd expect 24s to complete.

Raspistill gained the option to start in burst mode (which bypasses the preview phase) IFF all parameters are specified manually. raspberrypi/userland@2fe4ca3
You can probably do a similar thing under Picamera.