V4L2: Why image taken with shortest exposure-time looks way too brighter than auto-exposure mode?

When capturing image using the default auto-exposure-mode: $ v4l2-ctl -d0 --set-fmt-video=width=width,height=height,pixelformat=MJPG --stream-mmap --stream-to=auto_expo.jpg --stream-count=1 auto_expo.jpg shows: But when capturing image using the manual exposure, using shortest possible exposure value of 4: $ v4l2-ctl -d0 -c exposure_auto=1 $ v4l2-ctl -d0 -c exposure_absolute=4 $ v4l2-ctl -d0 --set-fmt-video=width=width,height=height,pixelformat=MJPG --stream-mmap --stream-to=manual_expo.jpg --stream-count=1 manual_expo.jpg shows V4L2 Values Before: $ v4l2-ctl -d0 --list-ctrls brightness 0x00980900 (int) : min=0 max=15 step=1 default=8 value=8 contrast 0x00980901 (int) : min=0 max=15 step=1 default=8 value=8 saturation 0x00980902 (int) : min=0 max=15 step=1 default=7 value=7 hue 0x00980903 (int) : min=-10 max=10 step=1 default=0 value=0 white_balance_temperature_auto 0x0098090c (bool) : default=1 value=1 gamma 0x00980910 (int) : min=1 max=10 step=1 default=7 value=7 gain 0x00980913 (int) : min=0 max=0 step=0 default=0 value=0 power_line_frequency 0x00980918 (menu) : min=0 max=2 default=2 value=2 white_balance_temperature 0x0098091a (int) : min=2800 max=6500 step=1 default=2800 value=2800 flags=inactive sharpness 0x0098091b (int) : min=0 max=15 step=1 default=6 value=6 backlight_compensation 0x0098091c (int) : min=0 max=1 step=1 default=0 value=0 exposure_auto 0x009a0901 (menu) : min=0 max=3 default=3 value=3 exposure_absolute 0x009a0902 (int) : min=4 max=5000 step=1 default=625 value=625 flags=inactive focus_absolute 0x009a090a (int) : min=0 max=21 step=1 default=16 value=16 flags=inactive focus_auto 0x009a090c (bool) : default=1 value=1 V4L2 Values After: $ v4l2-ctl -d0 --list-ctrls brightness 0x00980900 (int) : min=0 max=15 step=1 default=8 value=8 contrast 0x00980901 (int) : min=0 max=15 step=1 default=8 value=8 saturation 0x00980902 (int) : min=0 max=15 step=1 default=7 value=7 hue 0x00980903 (int) : min=-10 max=10 step=1 default=0 value=0 white_balance_temperature_auto 0x0098090c (bool) : default=1 value=1 gamma 0x00980910 (int) : min=1 max=10 step=1 default=7 value=7 gain 0x00980913 (int) : min=0 max=0 step=0 default=0 value=0 power_line_frequency 0x00980918 (menu) : min=0 max=2 default=2 value=2 white_balance_temperature 0x0098091a (int) : min=2800 max=6500 step=1 default=2800 value=2800 flags=inactive sharpness 0x0098091b (int) : min=0 max=15 step=1 default=6 value=6 backlight_compensation 0x0098091c (int) : min=0 max=1 step=1 default=0 value=0 exposure_auto 0x009a0901 (menu) : min=0 max=3 default=3 value=1 exposure_absolute 0x009a0902 (int) : min=4 max=5000 step=1 default=625 value=4 focus_absolute 0x009a090a (int) : min=0 max=21 step=1 default=16 value=16 flags=inactive focus_auto 0x009a090c (bool) : default=1 value=1