Friday, February 17, 2012

Valentine's Day Aurora

So I've finally put together the pieces of a time lapse video of the Northern Lights. On Valentine's Day after dinner I stepped outside to see the beginnings of the most amazing display I've seen yet this winter.  And it was only 20° F (above 0) outside! We've had some amazingly long stretches of -30° to -40 this winter, and that is not fun weather to set up any kind of camera equipment in... So I was thrilled to see temperature and northern lights together!

After getting my kids to bed it was about 10pm by the time I had strung together the 5x 50' and 1x 100' extension cords from the back of my van (sometimes being an electrician comes in handy!) and started setting up my tripod in the middle of the field in front of my house, where the camera could view both the neighborhood house lights (to give some context) & the northern lights. 

I often borrow this same old bogen tripod that is beastly heavy but very stable from a friend whenever I want to do something like this. It has a video head but that doesn't matter now - I quickly tighten down the camera and after some experimentation settle on the lowest position the tripod affords, breaking through the crusty snow to get a good bite in the field below. I've already inserted my canon power adapter in the camera and run through a quick refresher course of the various Magic Lantern settings (I'm still pretty unfamiliar with Magic Lantern, though I've used it to video a tutorial on faux wood grain which I will be sharing sometime in the future... Anyway hats off to the developers, it has given my camera a new spring in its step!). I also use the time in my warm van to take a few trial photos out of the window to get the basic settings down. The temperature outside has dropped to 10° and with a bit of wind you get cold quicker than you expect when fiddling with camera buttons.

Here's the setup, from my inadequate phone camera...!

I used manual focus, and the live view screen zoomed in 10x to check the focus - this is a great method whenever using manual focus when you have time for it... Especially when everything is pretty dark.

Here's a list of equipment & settings:
  • Canon 50D with Magic Lantern
  • Canon power adapter (ACK-E2)
  • Good solid tripod
  • F2.8 (it was pretty dark and I needed all the light I could get)
  • iso 800 (I tried for 400 but the shutter times it gave me were too long)
  • exposure: 8 seconds.
  • long exposure noise reduction ON
I used jpg rather than raw because I don't have the time to mess with raw on this project & my cf card is not big enough currently to take a night of raw photos one every 16 seconds - I ended up with 1967 photos from about 10pm to 7:45am. The camera was still clicking away as I walked up to it in the morning.

Pretty simple really! Magic Lantern is simple enough to use once I figured out that the Q button that is mentioned in the menus is the "func" button on the 50D... The intervalometer is better than the one that comes with the Canon utility - which only works if you are tethered. Thats because a) you don't have to be tethered and b) the photo count limit is much higher - Canon's EOS utility stopped at around 500 shots for me last time I used it.

In actual fact the camera lost a few seconds every time and so I ended up with more like 17-18 seconds between shots. I confirmed that if you were to set an interval of 5 seconds and specify a 9 second exposure (for instance) magic lantern would honor the exposure time (+noise r. if selected...) rather than sticking to its interval and cutting the exposure short.

The good part is that once I was happy with my setup I could just go inside and get warm - and forget about it until morning.

Next day, I used Time Lapse Assembler to put the photos together. It couldn't be simpler - and is also free!

The vertical resolution is NOT, as greyed out, 853 but turns out to be 1280. I chose 30fps because I wanted smoother given that in each photo the lights would have moved position quite a lot - because of that 8 second noise reduction: during those 8 seconds nothing is recorded and any movement is lost so the picture "jerks" to the next position. I will have to try a night without noise reduction! Sure would increase the number of stars :)

Then in iMovie I added sound and a few bits of text to give some sense of time passing as well as a black fade in and a white fade out - goes well with the fade to white effect you get at dawn!

Custom resolution in iMovie:

To get a custom resolution of 1920x1280 I started my project as 1080p. Then I selected the video clip (once imported to the project) clicked the settings gear wheel and chose "cropping and rotation". Then I selected "fit" instead of "crop" which was the default - it was going to chop 200px off the vertical resolution which I didn't want. Next time I might position the camera so anything important is framed by 1080 high, but this time I didn't want to miss out on seeing the buildings OR any of the northern lights themselves... Lastly in the top menubar I chose "share > export using quicktime", chose "movie to MPEG-4" (I wanted the h.264 codec) and then used the following settings (reached by clicking on "options"):

For "Data Rate" I used 300,000 k/sec which isn't entirely clear in the screenshot. This was arrived at after a quick googling of "best data rate for 1080p video" - I scanned the results and made up an average. Final file size was 104mb so while I may be off (and I in no way claim to be a codec/compression guru!!!) I am not far enough off to bother me. Quality is pretty good also.

I really love seeing the stars move. Its also interesting to see the street lights pick up intensity - I think some light fog settled at some point - and then I think some ice must have formed on my lens as I was getting more little red streak refractions from the light towards the middle/end. The motion sensor light on the right hand house obviously needs adjusting!

For next time, higher frame rate either from lack of noise reduction (would save me 8 seconds) or higher iso.

And I just installed Aurora Buddy on my phone so that I can have some heads up next time there is a good display on! You can set it to notify you if an aurora prediction above a certain threshold happens. I'll let you know if it works:)

thanks for reading! I'll be back with more fun stuff in the future! - Jon

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