今現状のv4l2でデバイスの情報をみると、こんな感じ。
$ v4l2-ctl -L
brightness 0x00980900 (int) : min=0 max=255 step=1 default=128 value=51
contrast 0x00980901 (int) : min=0 max=255 step=1 default=32 value=32
saturation 0x00980902 (int) : min=0 max=255 step=1 default=32 value=32
white_balance_temperature_auto 0x0098090c (bool) : default=1 value=1
gain 0x00980913 (int) : min=0 max=255 step=1 default=0 value=0
power_line_frequency 0x00980918 (menu) : min=0 max=2 default=2 value=2
0: Disabled
1: 50 Hz
2: 60 Hz
white_balance_temperature 0x0098091a (int) : min=0 max=10000 step=1 default=4000 value=4000 flags=inactive
sharpness 0x0098091b (int) : min=0 max=255 step=1 default=24 value=24
backlight_compensation 0x0098091c (int) : min=0 max=1 step=1 default=1 value=1
exposure_auto 0x009a0901 (menu) : min=0 max=3 default=3 value=3
1: Manual Mode
3: Aperture Priority Mode
exposure_absolute 0x009a0902 (int) : min=1 max=10000 step=1 default=156 value=156 flags=inactive
error 22 getting ext_ctrl Exposure, Auto Priority
led1_mode 0x0a046d05 (menu) : min=0 max=3 default=0 value=3
0: Off
1: On
2: Blink
3: Auto
led1_frequency 0x0a046d06 (int) : min=0 max=255 step=1 default=0 value=0この状態で
素の画像
$ fswebcam --no-banner -s Brightness=20% -s Gain=20% - | feh -
$ fswebcam --no-banner -s Brightness=100% -s Gain=20% - | feh -
更にパラメータを弄って露光時間を延ばすと……？
$ v4l2-ctl -c exposure_auto=1 -c exposure_absolute=312
$ fswebcam --no-banner -s Brightness=20% -s Gain=20% - | feh -
$ v4l2-ctl -c exposure_auto=1 -c exposure_absolute=624
$ fswebcam --no-banner -s Brightness=20% -s Gain=20% - | feh -
