How to Shoot a Time-Lapse: Intro to Interval and Exposure Settings and Techniques
There probably isn’t a human being on this planet who hasn’t, at one time, looked to the night sky in amazement. Today’s digital cameras now allow us to record scenes that escape our naked eyes. Here are some valuable tips to know before you head out to photograph your first star time-lapse.
The Benefits of Shooting in RAW for Star Time-Lapses
We are going to start with the simplest settings to remember when heading out in the evening to photograph stars and star time-lapses: shoot in RAW. I know RAW takes up more room. RAW takes more processing time. RAW, however, is everything that jpeg is not. It works better with noise reduction. It allows you to get the most out of your processing limits in post. RAW is also not compressed like a jpeg, so you will actually get the most detail possible when using it.
If you photograph stars with RAW you can also use a single photo out of a time-lapse series as a still photograph for prints. Also, don’t forget to use a full size RAW file and not a RAWs if your camera has it. This will allow you to photograph the largest pixel file. I use a Canon 1D X and it shoots an 18MP file. That file is over 5000 pixels on the long side, which can potentially yield a 5K video file in the end.
Good Glass Is Imperative for Star Time-Lapses
You need really good lenses for star time-lapses because it is dark out. I always tell my workshop participants that you should have a lens that has a max aperture opening of f/4 or better. An aperture of f/2.8 is much better than f/4 and f/1.8 and f/1.4 are better still. Lenses with these wide apertures are expensive, believe me I know, but BorrowLenses has everything you would ever need in the lens department, so give a good piece of glass a try on your next star outing. Here are their lens recommendations for shooting aurorae but they are good choices for any night sky shooting.
Settings You’ll Need for Star Time-Lapses
You need to set your camera to manual when shooting a star time-lapse (we’ll talk about when not to use certain manual settings later): manual shutter, manual aperture, manual ISO, and manual focus. I almost always shoot my stars with the lens wide open. If you are using an f/2.8 lens, then set that lens to f/2.8. I also set my lens’ focus to infinity. The infinity mark can be confusing depending on the lens you are using but it usually looks like a sideways “8” (meant to look like an infinite loop symbol). Read the owner’s manual for the specific lens to verify where true infinity for that lens is.
BorrowLenses tries to add manuals to every lens on their site but they can’t get them all so if you don’t see the option to download the manual on the site, try a regular online search. For some of my zoom lenses, true infinity is actually on a line that extends from my infinity mark on the focus ring.
As I said before, I almost always shoot my stars with the lens wide open. I say almost always because if I am photographing a time-lapse that begins as the sun is setting I will adjust my aperture, shutter speed, ISO, and focus for the sunset scene and then have to change those settings again as the stars begin to show. This type of time-lapse shooting scenario is typically called the “Holy Grail Time-Lapse” (more on this later).
Telephoto Star Trails vs. Wide Angle Trails
I haven’t tried to create a time-lapse video with a series of star trail photographs yet but it is on my list to see if I can make it work. However, I will shoot star trails, as well as pinpointed stars, when I head out to shoot just regular night sky photographs. Here is a little trick I use: I can make the star trails longer by using a telephoto lens instead of a wide angle. Going from a 16mm wide angle to a 200mm with the same 4 minute exposure yields dramatically different results in the quality of the trails themselves.
An Exposure Equation for Pinpointed Stars with Any Focal Length Lens
500 ÷ THE FOCAL LENGTH OF LENS = MAX EXPOSURE TIME
Example 1: 500 ÷ 16mm = 31.25 (or the closest shutter speed rounded down, which is 30 seconds) Example 2: 500 ÷ 35mm = 14.28 (or the closest shutter speed rounded down, which is 13 seconds)
There is a great tool for getting these calculations in the field. It is an app called PhotoPills. PhotoPills also has a website with the Spot Stars Calculator available for free. The app/website will also help you calculate the declination of stars for a more accurate number.
Numbers You Use for Video Shooting
Movies made today are typically shot at a film speed of 24 FPS (frames per second). That means you need 24 photographs for each second you want the time-lapse to occur. A 10 second clip needs 240 still photos. Now, I know you might be thinking that 240 photos doesn’t sound that bad–piece of cake, right? Enter technological limitations. It’s time to think about how often your camera can take an image, process out the noise, send that photo to the buffer, then to the card, and be ready to take another photo again automatically. This problem is further compounded at night when we are trying to eliminate noise from high-ISO photos.
Let’s say that we are shooting with a 16mm lens. We want pinpointed stars, which yields the need for a 30 second shutter opening (see equation above). This means your camera will need another 30 seconds to process out the noise before it can take another photo again. This now dictates that we can only take a photo every 60 seconds and finally, in turn, our little 240-frames-photoshoot becomes a 4 hour session out in the field for a short 10 second video! The PhotoPills App has a Time-lapse Calculator available online (and in the app as well).
Interval You Use for Time-Lapse Shooting
While photographing a star time-lapse, your interval is really dictated by your chosen exposure and camera buffer speed but if you decide to venture out at other times of the day, you really need to think about your interval. The interval is essentially the time frame that you will use to capture the movement of the subject that you are photographing. Think about how the sun moves across the land and how clouds roll in the sky. Your interval MUST exceed your exposure time, like mentioned above, in order to keep your time-lapse recording going. A good rule of thumb is to set your exposure to 50% of your interval time.
Here are some example interval times for various shooting scenarios:
15 – 60 Seconds: Moving Shadows, the Sun Moving Across the Sky, Stars
1 – 3 Seconds: Sunsets, Sunrises, Slower Moving Clouds, Crowds, Moon and Sun at Horizon
1 Second & Faster: Moving Traffic, Fast Moving Clouds
The Holy Grail of Time-Lapse
Remember at the beginning of this article I briefly touched on the “Holy Grail of Time-Lapse”? Most time-lapse photographers consider the Holy Grail Time-Lapse to occur when you photograph sunset through darkness when the stars begin trailing across the sky. They say this because it is actually the hardest time-lapse scenario to get right. You need to take into consideration all of the tips that I have mentioned so far to pull it off correctly, plus think about a few new ones.
Whenever I photograph stars for time-lapse, I set my camera to manual. I manually adjust my aperture to my lens’ widest opening (f/2.8). I set my shutter according to my focal length (that 500 ÷ lens focal length = maximum exposure time equation). I set my focus to infinity and usually tape it there. I lock my camera down on a tripod. And finally, set an interval (either on an intervalometer remote or in-camera) that is double what my shutter speed is set at. This all works really well when it is completely dark out. Then enter sunset/sunrise. When you are photographing sunset/sunrise, the light is changing quickly. If we keep our camera settings at full manual, the outside light will change too quickly and our camera will start recording completely dark or way overblown exposures. In addition to this issue, the sun could vary the light in your scene, which would cause another scenario that time-lapse photographers hate: flicker.
Flicker happens during a sunset/sunrise as light changes and the camera is set to manual and can’t adjust itself to compensate. When you play back the photos in a movie, you get a “flickering” effect as the photos jump between the lighter and darker exposures. How do we fix this? For the sunset/sunrise portion of our time-lapse, we set our cameras to Aperture Priority. This allows the camera to immediately adjust the shutter length right before the exposure is triggered. In Aperture Priority, you set your aperture and your camera chooses a shutter speed based on its own exposure metering. To change to Aperture Priority/A/Av mode, either turn to A or Av on a dial on the camera’s body or hold down the Mode button and spin your settings dial to toggle to Av.
To get started, set your camera to Aperture Priority mode and then choose your aperture setting as you would to record any landscape photo. A smaller aperture opening works here because you will see everything that is in your foreground at this point. Now remember, you need to switch all of your exposure settings back to manual as your scene gets dark, which means manually opening your aperture. The foreground landscape will likely be obscured in darkness, so depth of field isn’t too much of an issue – but adjust this tactic according to your needs. If you are proficient with your equipment, this switch will only take a second or two and that amount of time isn’t going to ruin your overall time-lapse sequence. You are letting your camera control your shutter speed as the light transitions to night and once night hits, you can take over and set the camera back to fully manual operation since you can get away with static settings while it is dark.
Once you download your photos and begin to work on them, a software that works really well for assembling the time-lapse (but also has the ability to fix most flicker issues with a de-flicker component as part of its workflow) is LR TimeLapse. It makes your job really easy when it comes time to merge all of your photos together into a video.
Easily recording how the stars move overhead wasn’t really possible until the invention of the digital camera. This technology has put so many different aspects of photography into virtually anyone’s hands. While there are many things to consider for creating a successful star time-lapse, you can always start simple and progress into the more difficult technical aspects. Nothing spices up a home video or keynote like a little bit of motion video, especially if that video highlights the sun and stars in motion.