Sensor Manual Gain Control

# This work is licensed under the MIT license.
# Copyright (c) 2013-2023 OpenMV LLC. All rights reserved.
# https://github.com/openmv/openmv/blob/master/LICENSE
#
# Sensor Manual Gain Control
#
# This example shows off how to control the camera sensor's
# gain manually versus letting auto gain control run.

# What's the difference between gain and exposure control?
#
# Well, by increasing the exposure time for the image you're getting more
# light on the camera. This gives you the best signal to noise ratio. You
# in general always want to increase the expsoure time... except, when you
# increase the exposure time you decrease the maximum possible frame rate
# and if anything moves in the image it will start to blur more with a
# higher exposure time. Gain control allows you to increase the output per
# pixel using analog and digital multipliers... however, it also amplifies
# noise. So, it's best to let the exposure increase as much as possible
# and then use gain control to make up any remaining ground.

import csi
import time

# Change this value to adjust the gain. Try 10.0/0/0.1/etc.
GAIN_SCALE = 1.0

csi0 = csi.CSI()
csi0.reset()  # Reset and initialize the sensor.
csi0.pixformat(csi.RGB565)  # Set pixel format to RGB565 (or GRAYSCALE)
csi0.framesize(csi.QVGA)  # Set frame size to QVGA (320x240)

# Print out the initial gain for comparison.
print("Initial gain == %f db" % csi0.gain_db())

csi0.snapshot(time=2000)  # Wait for settings take effect.
clock = time.clock()  # Create a clock object to track the FPS.

# You have to turn automatic exposure control and automatic white balance off
# otherwise they will change the image exposure to undo any gain settings
# that you put in place...
csi0.auto_exposure(False)
csi0.auto_whitebal(False)
# Need to let the above settings get in...
csi0.snapshot(time=500)

current_gain_in_decibels = csi0.gain_db()
print("Current Gain == %f db" % current_gain_in_decibels)

# Auto gain control (AGC) is enabled by default. Calling the below function
# disables sensor auto gain control. The additionally "gain_db"
# argument then overrides the auto gain value after AGC is disabled.
csi0.auto_gain(False, gain_db=current_gain_in_decibels * GAIN_SCALE)

print("New gain == %f db" % csi0.gain_db())
# csi0.gain_db() returns the exact camera sensor gain decibels.
# However, this may be a different number than what was commanded because
# the sensor code converts the gain to a small and large gain value which
# aren't able to accept all possible values...

# If you want to turn auto gain back on do: csi0.auto_gain(True)
# Note that the camera sensor will then change the gain as it likes.

# Doing: csi0.auto_gain(False)
# Just disables the gain value update but does not change the gain
# value the camera sensor determined was good.

while True:
    clock.tick()  # Update the FPS clock.
    img = csi0.snapshot()  # Take a picture and return the image.
    print(clock.fps())  # Note: OpenMV Cam runs about half as fast when connected
    # to the IDE. The FPS should increase once disconnected.