Things I Wish I'd Known Earlier

Having a fascination with weather, I have always enjoyed seeing time-lapse movies of the sky, and having recently acquired a camera capable of doing this, I jumped in and started making some myself. Here is an example that I uploaded to Youtube. I recommend that you view at maximum resolution possible (720p).

However, there are many factors involved in making such a movie, and it requires not just the right equipment, but also quite of lot of attention to detail. It obviously helps to have a technical bent to start with.

The camera I have is a Canon EOS 550D. This is a digital SLR. Although this camera is able to take HD video footage, creating time-lapse videos does not involve using it in video camera mode. Rather, what you have to do is to take a series of timed individual photos, and only after the whole sequence has been taken do you perform the final steps to assemble to individual shots into a movie using software on your computer.

Some things to be aware of:

• The camera must not move during the filming, which may last several hours of more. I use a tripod to do this – and take care not to move or knock it after the photo shoot has started.
• If filming through a window, make sure the glass is clean, and keep the camera as close as possible to the glass. After my first couple of efforts I noticed some blotches on the movie which were only visible when watching the playback – they weren’t at all apparent until there was coud movement happening behind it.
• If filming through a window, minimise all possible reflections. Cover or block or reduce all other light sources in the room if at all possible. Again, on my first efforts I noticed some reflections which only became apparent when watching the playback. That can be frustrating if you’ve spent several hours recording before you see it.
• The shutter timer control must be automatic or by remote control, as touching or adjusting the camera during shooting will inevitably move the framing and cause jittery movements in the final video. The camera came with software which allows this to be done by connecting the camera to your computer by USB cable, and then setting up the utility software to take shots at the required interval. I used this initially, and it worked well enough, although it requires you to keep your computer running the entire time of the shoot. Later I bought a separate battery-controlled timer device which plugs into the camera and is a much more lightweight solution (shown in photo above).
• The camera’s auto-focus control cause the picture frame size to change by small amounts. For my first effort I left it on, and the picture jumped in size a lot – not a good result. Make sure you focus the camera before you start the shooting (for example by half-pressing the shutter button), then set it to manual focus.
• Depending on what you are shooting, you may or may not want to let the camera automatically adjust to light changes. For weather time-lapse I have found that automatic camera operation works quite well. However, for sunrise or sunset time lapse not quite so well, because as the camera adjust for light levels, the impression of increasing/decreasing light levels are somewhat lost.
• Unless you have a power supply connected to your camera, the number of pictures it can take will be limited by how long the battery lasts. I have found that I can take about 1500 pictures or so with one full battery charge. If you render your finished video at a fairly standard 24 frames per second, this will result in a maximum duration of about 60 seconds for a single video sequence. Changing the battery will definitely interrupt the sequence, and very likely also cause the camera’s viewpoint to shift noticeably too. If you want more than this then you could buy a battery shoe, or if you are shooting from indoors you could consider using an external power adapter – both of which require you to purchase optional add-ons, and are not necessarily cheap.
• Before you start shooting, set your photo resolution mode to low. You may be taking thousands of pictures, and unless you want to treasure and reuse every last frame, there is no point having each photo consume 20MB disk space when it might only 0.5MB might be necessary. On the Canon 550D, the smallest picture resolution (“S”) is 2592 x 1728, which is more than even full HD video requires (1920 x 1080), and using anything more than this will simply be resized down during video rendering phase anyway.
• If you want your final movie to be in HD format, then the photos you are taking will likely have to be cropped at the top and bottom. HD format has an aspect ratio (width:height) of 16:9, whereas the Canon photos have a ratio of 3:2. This means that my photos all lose 15.625% of their height, split evenly between the top and bottom (ie. “letter-boxed”). When setting up your shot there is no tool for visualising this – you just have to estimate and hope you get it right. I like to have the horizon/skyline visible in my weather time lapse videos, so I need to make sure that I am allowing this to be seen within the letter-boxed area.

How I assembled the individual photos into a movie (using Mac computer):

I used Time Lapse Assembler (Mac, freeware) although apparently it would also be possible to use Quicktime Pro (paid license required).

This allows you to select

• The folder which contains all of the photos you wish to assemble into a video
• Video codec – I have always used h.264, which is good for YouTube, for example.
• Framerate – Standard frame rates would be 20, 24 or 30 fps. I typically choose 24 fps.
• Dimensions – This is where you can choose what size your movie will be. I typically have the resize option on, and also scale proportionately on (to avoid distorting the images). In this case you can only specify the width desired, so to get a particular desired height (eg. 480, 720, 1080 which are standard Youtube sizes) you need to know your photo aspect ratio and calculate the required width to enter. For example, my photos have a 3:2 aspect ratio, so to achieve a height of 720 I would need to specify a width of 1080.
• Quality – I experimented with this setting, and generally use “High” for viewing the video on my own computer. However, this may also depend on what type of subject you are filming. I find, for weather time-lapse, that the image detail is important. If you have a less demanding subject then lower settings may also be ok, and this will result in smaller video file sizes.

Note that, as far as I can tell, Time Lapse Assembler doesn’t allow you to crop your photos to fit HD format. Instead it only resizes the images, retaining their original aspect ratio (if “Scale proportionally” is on) or else distorting the image the fit the desired aspect ratio (if “Scale proportionally” is off). However, there are other ways of achieving this. For example the Mac has a built-in tool called “Automator” which does allow you to build a script that will crop all the photos for you automatically, which you can use as a step before you use Time Lapse Assembler.

A final step (optionally) is to edit your raw video and compose it into an edited masterpiece using some kind of video editing software. If you only want to do basic editing such as adding titles and a music track, as I did in the video shown above, you can probably use whatever video editing package came with your computer. I used iMovie. Of course this requires a whole new level of learning, and it is beyond what I wanted to relay here, but at least you can know that a novice such as myself didn’t find it too hard to arrive at a simple, but fully finished product.