This is a bulb ramping test I did of my pond last night. I wanted to be sure I had timing and exposures down well for this time of year with my Promote Control. I used 20 second intervals and manual exposure up until civil dusk at 9 PM, changing the exposure by 1 stop every 5 to 10 minutes as necessary to keep it around a proper exposure. I started at f/2.8, 1/1000, ISO 200 at around 7:30 PM and was up to f/2.8, 1.3 seconds, ISO 200 at 9 PM. At 9 PM (civil dusk) I started a bulb ramp with the Promote Control until the difference between nautical and astronomic dusk (9:50 PM and 10:58 PM respectively), setting the ramp to climb to f/2.8, 30 seconds, ISO 2500 by 10:24 PM. Around 1 AM I went out to swap out batteries and reverse the ramp starting at the difference between astronomical and nautical dawn (02:09 AM and 03:16 AM respectively, so the ramp started at 2:42 AM) to the same exposure at civil dawn (04:06 AM) that I’d used at civil dusk (f/2.8, 1.3 seconds, ISO 200). At 4:06 AM I switched to program mode and let the camera handle the rest of the exposures. The exposure it chose was exactly f/2.8, 1.3 seconds, ISO 200 so I knew my bulb ramping had worked well!
For post processing I removed the steps of my manual ramping before dusk and the flicker of auto exposure after dawn with LRTimelapse and changed my white balance via keyframes with Lightroom. This resulted in the very smooth timelapse you see here. Unfortunately I made a small gap at 1 AM when I switched batteries and reversed the bulb ramping procedure. I’m not quite proficient enough yet to do it very fast. There was also some pretty heavy cloud cover so the stars aren’t all that interesting.
Hopefully this helps others strugging with times and exposures for bulb ramping. It’s best to take some still shots the night before your timelapse if possible to figure out your exposures and use an app like SkySafari (iPhone) to figure out your dusk and dawn times for your date and location. Moon brightness and cloud cover will also affect your exposure (if you aren’t in a city and have very little light pollution).
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