autoFramerate.py

from picamera import PiCamera, mmal, mmalobj as mo
from time import sleep

#camera = mo.MMALCamera()
camera = PiCamera(resolution=(2592, 1944))
camera.start_preview()

preview = mo.MMALRenderer()
encoder = mo.MMALVideoEncoder()

camera.preview.close() # .disconnect()

camera._camera.outputs[0].framerate = 0	#not limiting the framerate with value 0

ex = camera._camera.control.params[mmal.MMAL_PARAMETER_EXPOSURE_MODE]#  switch to exp_mode night
ex.value = mmal.MMAL_PARAM_EXPOSUREMODE_NIGHT
camera._camera.control.params[mmal.MMAL_PARAMETER_EXPOSURE_MODE]  = ex
#connect my preview
preview.connect(camera._camera.outputs[0])

sleep(10) #now its adjusting

# but when we take pictures here, our preview gets destroyed :(
self.camera.capture("test.jpg", format='jpeg') # no matter if use_video_port=True or not
print ('exposure: %d ms  gain: %d') % (camera.exposure_speed, camera.analog_gain)# thats what i wanna find out at beginning 
sleep(10)
#now preview is gone because we set it up manualy and didnt use the 'wrapper' class i guess
# just tested again and now it seems to work....more testing needed here

preview.disconnect()
preview.close()
camera.close()