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October 14, 2017

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Redefining the limits of astro-timelapse: Why not zoom in a bit?

April 29, 2017

As there are hundreds of original and extraordinary time-lapse films featuring our home galaxy, they almost all offer the same: a wide-angle view of the milky way against various foregrounds. As a consequence does it sound so crazy to want to break the routine by not abiding by the rules? Could it be the start of a new trend? It is in any case a brand new look on how to make astro-timelapse, and here is how...

 

 

Astro-timelapsing is a discipline that requires a lot of patience, self-discipline and self-teaching. It also requires making a lot of sacrifices to go out and shoot at all costs. I don't know of any amateur or professional astrophotographer that would tell you otherwise. It just takes time and an awful amount of practice. You have to get to know your gear's capabilities and limitations. Since it is a field of its own- stacking a series of single astrophotos back to back into a movie sequence, there isn't too much room for tweaking and improving your astrophotos, at least in the same way as a still picture. As a beginner, you will sooner or later find out that you are in a constant struggle with yourself and your photos. Namely, noise versus light and detail. See, a film makes noise (a reading pixel value error) 'alive' and more visible, as the pixel value has more chance to change from one frame to another, especially if the noise is high. I can already hear you tell me that you can correct it, and yes you can and you have to! However that's where the first limitation pops up: you can't just apply a whole load of noise correction just like a still and expect to get a cleaned sequence, no matter how powerful your software is. Besides, as you turn on the noise reduction button, you dramatically wash out the precious details of your shots. You find yourself facing a gut-wrenching dilemma: sacrificing detail or cleanliness? 
As you will never completely be out of the woods on this one, there are ways of significantly turning the odds in your favor and avoid yourself wasted hours of mind-boggling post-production that would turn your raw photos into only hardly usable time-lapse. That's where the 'practice makes perfect' comes into play...

 

 
1) Get away from light pollution at all costs
As you are shooting your time-lapse in a very light polluted area, your milky way will be so washed out that you will be tempted to bump up your clarity / contrast / dehaze way too much, causing heavy noise and resulting in unusable footage. Get away from light-polluted areas to gain in detail and contrast without compromising the noise level! You will be surprised how 'easy' your astro-life gets when you get to pitch black skies...

2) Put all the chances on your side: choose your lenses carefully!

Since noise is such a sensitive consequence in astro-timelapsing, you wouldn't want to trifle with this one. Even though it is extremely hard to find the perfect settings (ISO, shutter speed, aperture) and not every shoot is the same, there is a pattern you can follow. Find your camera's optimal ISO (the ISO setting for which your sensor commits the least pixel reading error while keeping the widest dynamic range, e.g. without blowing highlights in stars) and don't budge! You can read a very interesting article from Petapixel that can help you find this optimal ISO, or even this one if you own a Canon camera (click here). Now the shutter speed will also determine how much light gets in, and while the star trailing issue is a bit less important in time-lapse than for stills, you will still lose detail and clarity if you go beyond the rule of 500/focal length (+- APS-c or FF sensor). My advice: stay precisely at the shutter speed value given by the rule. Last but not least, the aperture is the setting that will make the difference in astro time-lapse. With the ISO and shutter speed now fixed, you will need to find the lens with the lowest minimal f-stop, while not compromising sharpness and distortion. For clean and pin-point stars in stills, you will need to stop up to 2-3 stops higher than your maximum aperture, but not necessarily for astro-timelapse, and that's where you can majorly improve the quality of your single shots, if you choose the best lenses. My advice: find a lens with a minimum f-stop of 1.4 or 1.2 that has maximum sharpness and the least distortion/vignetting, and set it only one stop higher. In this way you are getting rid of a some vignetting and gaining in corner-to-corner sharpness while still taking advantage of a ultra-wide aperture. Samyang/Rokinon and Sigma offer, in my opinion, the best f-stop to sharpness/glass quality ratio on the market as for now, and hey, they're relatively cheap! Here is an excellent article by Ian Norman (Lonely Speck) about the best lenses for astrophotography to help you get started.

 

3) Finding a good camera for astro-timelapse...

At night, the number of pixels in your sensor is far from being the most important, and a 12MP camera can outperform a 42MP because it has more effective pixels, so less noise (that's why lenses are so crucial in the astro-timelpase). Since you are still in the mindset of finding the best balance between noise and detail, you want to get the camera that performs the best in low-light conditions, that is to say that has the most pixel-effective sensor. Of all the cameras I have tried/seen in action for astro-lapse, here are some of the best: Sony a7s (still my favorite) and a7, Canon 5D mark III and IV, Canon 6D, Canon 1Dx, Nikon D700, D810 and D3200. 

4) During the shoot...
Before choosing the location, you will have to do a lot of digging and thinking during daytime. You have to imagine the development of the sequence in your head, keeping in mind the subject you want to shoot. You can find apps on the app store (Star Walk, Sky guide, Sky Live...) that will help you determine the movement of the night sky according to the rotation of the Earth, but also shooting conditions (cloud cover, moon...). As you set up your gear for the night-time shoot, you will probably need the following: an intervalometer shutter release, a sturdy tripod or slider, a lens heater (prevent due formation), an empty SD card (some, including myself, will know what I mean), and full batteries. What interval should you choose? It is totally up to you and your camera capabilities. If you want your milky way to move slowly across the sky, then you can use a 3-5 second intervals (less than 3 seconds will generally affect the exposure time on the next photo and add annoying flickering for most cameras and slow SD cards). If you now desire a speedy milky way, you can try 15-30 seconds or more. Be careful though, you will have to take your focal length into account: 30 second intervals at 85mm will have your milky way disappear way too fast from your frame. Then again, you should practice and find what suits you best! 
Once you press on the intervalometer, do not touch your setup under any circumstance, bounce next to it, or do anything that would cause vibrations (I also advise against shooting in strong wind situations, I know what I am talking about living in Denmark!). The slightest displacement of the rig will result in a visibly blurry image and can potentially ruin several hours of work. 

How many shots? Well, again it is up to you and it all depends on your needs. Since you will assemble your pictures back to back, you will need to define a frame rate (number of frames per second). The following are some examples of comfortable and usually used frame rates: 23.97 or 24/25 fps (frames per second) for cinema-like look, 30 fps for a basic movie look,  or even 60 fps for a very fluid look. The more you increase your rate, the more pictures you're going to have to take for the same result. I generally produce at 25 fps, so I generally take about 200 pictures, giving me an 8-second sequence once stacked. My advice: take as many shots as possible (maybe between 200-400), because you might encounter some vibrations anyways or something you want to remove in post-processing. 

 

5) Find a consistant and lossless workflow

It might sound silly, but your final sequence and production will be tremendously affected by how consistant you are. Practice, see what settings are best for your taste and try to find a post-production workflow that you are comfortable with. Even if amateurs and professionals are constantly trying to find new softwares and post-prod tweaks to better their sequences, you have to start somewhere!

First, shoot in RAW (lossless format). Import and edit your pictures in any software that you like (Lr, Capture One...) and export your pictures in JPEG (highest quality). You can try and export in TIFF if really you want a lossless quality, but your 10-second sequence will turn into a 20Go! Assemble your single frames in a software. You can use LrTimelapse (one of the best on the market because it lets you work hand-in-hand with Lightroom, and allows you to correct noise, flickering, adjust temperature and brightness...). I personally use 'Sequence' for quick rendering. Before exporting to these softwares, you might want to resize your pictures in your editing software, choosing the area of interest. Indeed, the modern monitor and TV formats being squeezed into a 16:9 ratio, while your pictures are 3:2 or 4:3, you will have to make them fit into your TV or screen without stretching any pixel. Besides, most assembling softwares will randomly crop at the center and won't let you chose the area. With that being said, you will also have to chose a rendering quality (resolution of your sequence). Whilst most softwares will include standard presets (720p, 1080p, 2K, 4K, 8K, custom...), you have to compare if the initial dimensions of your exported pictures fit the dimensions of the chosen resolution. For example if you are exporting in 4K (UHD) that has a resolution of 3840 pixels in length by 2160 lines in height (8.3 MP at 16:9 ratio), you need to make sure that your exported pictures are at least 3840 pixels long and 2160 pixels high. Most DSLR's having a sensor more than 12MP are capable of producing 4K timelapse nowadays. 
Choose the exporting codec (encoding format): it will determine the final quality of your sequence. Increasing the quality means increasing the place the time-lapse will take on your computer. You need to find a good compromise between the two. MPEG and MP4 are old codecs that compress your video so much that you considerably lose in quality. If you want a decent codec that doesn't take too much space and preserves at least 50% of the initial quality, use H.264 or H.265 (newer versions of MPEG). I personally use Apple ProRess 422, which turns an 8-second sequence into a rough 1Go file and has excellent professional-looking quality. The last step is exporting and storing your sequence for future use in a film!

 

 

However demanding astro-lapse can be, it is probably one of the most rewarding sub-disciplines of photography and the one that brings the most joy/wow-effect after long hours of shoot. You learn so much about yourself, your limits, your patience, the capabilities of your material, and the wonders of the sky. It all began for me as I first settled down in Denmark four years ago. I was teacher at a school that offered a photography and film production extra-curricular to the students, and I first put my hands on a camera with Frederik Bramming, the school's film teacher, as we were out wondering how you could possibly take pictures of the night sky. The more I watched beautiful time-lapse videos of the milky way, the more I wanted to do the same. I got addicted since then and I have come a long way now, making tons of mistakes and faux-pas, facing a lot of challenges and making wrong decisions. I think everyone will agree that it is not about copying and reproducing the others, but more about enjoying what you are doing and creating your own style/artwork. So I decided to think anew...

 

This stunning video from Randy Halverson remains one of my favorite astro-lapse and source of inspiration to date.

Most astro-lapses available to watch on the web, as wonderful as they can be, present in my opinion very little variation. Almost all of them primarily consist of a wide-angle view of the milky way moving behind various foregrounds. Don't get me wrong, they are gorgeous, but I find them very limited, knowing all the potential tools, techniques and effects one can use. Astro-lapse is after all a very recent new hobby and market. You can find some hints in Randy's astounding video where he really tries to vary perspectives, focal lengths and subjects. This is what put me on the right path: extending the limits of astro-lapse! Why stay at wide focal lengths with flat-looking scenes when you can use all the potential of your aperture ring (beautiful bokeh, perspective given by low aperture on narrow-angle lenses...)? Why not zoom in? Why not look at the milky way from new angles? Why only restrain ourselves to our home galaxy when our night sky is teeming with other exciting objects?

I started thinking about making time-lapse of deep-sky objects about two years ago when I bought my iOptron Skyguider tracker. I would experiment and track the Andromeda galaxy moving in front of rocks, monuments, trees, behind northern lights. I expanded the boundaries of wide-field astro-lapse (10-35mm) to a more middle (50-85mm) and narrow-field of view (> 85mm). It gives a lot of new options and reveals the true beauty and detail of our galactic core fore example. Denmark is rather limited in terms of dark skies and weather, so I haven't produced that many, but I really want to make more and unlock new possibilities. Once you have found consistency, proficiency and comfort in your workflow, it just allows you to come up with super sharp, colorful and never-seen-before sequences. I have been working extensively for two years on a astro-lapse project and the main canvas of the project is based on our galaxy and their neighbors (Andromeda, the Magellanic clouds..), but also a lot more deep-sky objects like nebulas, star clusters etc… It was the perfect opportunity for me to showcase a novelty in this field, while pioneering new horizons that other astro-lapsers will hopefully help broaden. 
 

                                                WATCH GALAXIES VOL. 1 in 4K:

 

Amateurs and professionals will certainly recognize a multitude of deep-sky objects like the North-American nebula, the Orion nebula, the Rosette nebula, the Carina nebula, the dark horse nebula, the Andromeda galaxy in different situations like photobombed by northern lights or moving behind the tree canopy, the majestic milky way core either rising or in very fine detail moving fleeting gently across the nigh sky… You will still find some wide-angle milky way scenes, because you just cannot pass on them!

 

My two favorite parts of the project (and the most technically difficult) were shooting the Andromed