This method shifts from manual mode to bulb mode when the scene darkens. AutoRamp will adjust the Tv, Av and ISO to maintain a good exposure. To shift modes, it requires a Group 1 or Group 2 camera or a Group 3 camera without a mode dial. Use this when the light is changing. Uses single release for bright daytime scenes and bulb for darker scenes. This method can be used for sunrise/sunset transitions. Use GBDeflicker in post to remove any traces of flicker resulting from Tv stepping.
As the sun sets the Tv is increased in 1/3 stop steps until it is below the “bulb switch” time. Then the shutter is changed to bulb mode and the bulb time continues to increase gradually. Whenever the bulb time exceeds the Av shift time, the Av f-number is decreased in 1/3 stop steps up to its maximum value. After the Av reaches it minimum f-number, the ISO is increased in steps to 3200.