The two most frequent questions I’m asked are “How do I make a 3-month construction time-lapse?” and “How do I make day-to-night time-lapse?” I’ve tried my best to answer the construction time-lapse methods question before, but I haven’t talked much about day-to-night.
The day-to-night question is usually asked by someone who wants to start making time-lapse videos but doesn’t have any experience yet. This always reminds me of the 10-year-old in one of my woodworking classes years ago who wanted to make a full sized catamaran during his two week class. I applauded his confidence but eventually steered him toward making a model airplane. There’s a reason day-to-night is referred to as the “holy grail” of time-lapse. It can be incredibly difficult. That said, there are at least three proven methods for making day-to-night time-lapse.
The Cross Fade Method
This is the easiest method by far and is pretty effective. I’ve seen this used not only in web videos but on TV shows and in movies. To create the cross fade, you simply shoot a time-lapse sequence during the day, shoot another at night, and use any number of video editing programs to create a fade between the two sequences.
The method works so well that most people won’t realize what happened and will think it’s a single sequence. Only us time-lapse enthusiasts will notice the editing. In order for this method to work, you’ll need to keep the camera positioned in one spot the whole time or be able to line up the shot exactly a second time. I’d suggest taking photographs for the day sequence over a period long enough to see either the motion of the sun toward the horizon or shadows growing longer. This probably shouldn’t be in the last couple hours of daylight because you’ll have exposure problems as the area grows darker. A neutral density (ND) filter could help you drag the shutter for multi-second exposures. This is important because your nighttime shots will likely need multi-second exposures due to low light conditions and you’ll want your sequences to have continuity. Again, it probably won’t matter to most casual viewers but will simply give your video that extra push from ordinary to excellent.
The Auto Exposure Method
This method is much more difficult and requires good equipment and software but I’ve had some success with it. In short, you’ll let your camera determine the settings of each shot and then clean up the final video in post production.
My original method for this was to use my Canon 60D set to aperture priority and then lock down all other settings except shutter speed. The downside to this method is that shutter open times are inherently variable and exposure is too dark and too light at time. The positive is the end result can look better than the cross fade method. I used a similar method with the Canon 5d Mk. III but set the camera to full manual mode and let the ISO self-adjust. This meant the shutter time was consistent throughout. The reason I could do this on the 5D and not the 60D was that the 5D had much less noise in high ISO ranges. Recent advances in high ISO mean this could be my preferred method in the future. The shortcoming of the 5D over the 60D was that the light sensor wasn’t as good and so the exposures weren’t as consistent. This might be due to the particular cameras I was using. I haven’t heard anything else bad about the 5D Mk. III’s light sensor.
If using the auto exposure method, be sure to shoot in RAW and open the aperture wide to prevent excessive flicker. There will still be high levels of flicker, so you’ll have to use software such as LRTimelapse when you process the photos. LRTimelapse and similar software work with RAW files to smooth transitions between individual photos in a time-lapse sequence. This helps reduce flicker and will let you set white balance key frames in order to keep colors looking natural.
You’ll need to set your exposure reference point before beginning the shoot. I’d suggest avoiding using the sky as your reference because it changes too quickly. Similarly, any area with artificial light will likely have a harsh exposure change when the lights come on. This may take some testing, so I suggest first trying something with a neutral tone that won’t get direct sunlight. Also remember that the time between photos needs to be greater than the longest possible shutter time.
The Bramping Method
Bulb ramping, or bramping, is a way to adjust settings between shots by shooting in bulb mode and making manual adjustments throughout the shoot with an external device. These devices range from simple and inexpensive to professional level. It seems a new time-lapse toy is introduced on Kickstarter every few months that includes bramping as an added feature. I haven’t written much about bramping because I haven’t tried the method myself but it’s the go-to method for many professionals.
I’ve heard the best method for bramping is to try making adjustments in full steps so you’ll know how much to adjust the photos before and after the transition. Just like the auto exposure method, you’ll need to shoot in RAW and use specialized software to create smooth transitions. The upside to the bramping method is control. It’s possible to use ND filters during the day shots in order to match the shutter time of night shots. The downside is the amount of expertise required and a lot more hands-on time with your camera.
Whatever method you choose, try not to get too disappointed if your first attempt doesn’t look perfect. This is one of the hardest things to capture in time-lapse but also one of the most rewarding. If you get a good result or just want some suggestions, feel free to link to your video in the comments.