Here's how i shut down the OV3660 lens....
// Put Camera Module into Standby Mode
sensor_t * s = esp_camera_sensor_get();
s->set_reg(s,0x3008,0xff,0x01);//banksel --- ? Is this needed for ov3660? Is there only 1 bank
s->set_reg(s,0x3008,0xff,0x80);//reset (we do this to clear the sensor registries, it seems to get more consistent images this way)
s->set_reg(s,0x3008,0xff,0x40); //stand by (sensor, register, mask, value)
I reboot the camera to turn the lens back on.. .but there are registry setting that can be invoked to restart the camera module. see Omnivision OV3360 spec for registry settings.