New Time Lapse
http://vimeo.com/26451468 I’ve spent the last day working on a new time lapse and so I thought I would do a quick write-up of my workflow. I’m always looking to improve my technique and so hopefully someone else will find this helpful and/or share some tips with me.
To begin, I shot this as a series of stills, JPEG, 21 Megapixel, fine resolution @ 1 shot ever 2 seconds. I did not shoot in RAW because the resulting files take much longer to process than the JPEG files do. If I was shooting for National Geographic I would – but I’m not.
My goal was to take a nice video of the sun set. As I was considering wrapping up shooting I noticed that the moon was rising over campus and was entering the frame. Unfortunately, I was shooting with a polarizing filter and that significantly cut down on the incoming light. I couldn’t remove the filter between shots because if the camera moved or the lens settings changed in any way the final video would have a jump in the final product. Of course, shooting at night, at f/8 with a polarizing filter causes other problems. The exposure time went from 1/800 in the daylight to 1.5S a dark. To compensate, I had to stop the time lapse at two points and bump up the ISO from 800 to 2000 to 3200. This added noise to the scene that I will address later.
Once I was done, I had nearly 20,000MB of photographs to work with. I imported them in to a new Aperture library and played with the settings until I achieved a look that I liked. I cropped the frame to 16×9 and applied the adjustments to all of the images. From there, I exported the frames as a series of images @2,000 pixels wide. 1080P HD video is 1920 pixels wide so this gave me a slight buffer when working with the sequence in After Effects.
In AE CS3, I imported the sequence as a new clip and setup a new composition for the video. From there, I used motion stabilization to analyze and remove most of the jitter caused by the wind. I selected two targets on opposite sides of the frame to calculate rotation and let AE do the rest. Next, I applied a noise reduction filter and I used a non-default temporal setting (5 frames, I believe) to help identify the noise in the higher-ISO sections. One of the benefits of shooting @ 21 Megapixels is that when you scale down the image, you are effectively oversampling the image and reducing the signal to noise ratio. The resulting frames were still pretty grainy so that is why I elected to use the noise reduction filter.
Next up, I enabled frame blending and remapped the time to 50%. The resulting video was too long to be enjoyable so I had to speed it up. This also had the added benefit of removing some of the flicker caused by the camera.
When you are filming a time lapse, you have a critical choice to make: do you manually set the exposure or do you let the camera? If you manually set the exposure, the resulting video will not flicker. This is great for clips where the lighting does not change dramatically. Unfortunately, in a sunset clip like this, you pretty much have to let the camera meter each and every frame. Each photo is slightly different: trees are moving, lights are reflecting off buildings and people are walking throughout the scene. This causes the camera to meter some frames brighter than others and the result is a video that flickers.
There are plugins to remove time-lapse flicker but I have not experimented with them too much. Apparently the color stabilizer filter can help with some of this but I’ve had limited success. Thankfully, speeding up the clip with blending helps to a degree.
Lastly, the resulting composition was exported as a high bit rate video and sent to Vimeo.