After my last post on “How to shoot the night sky?“, hope you got some chance to get out there to shoot some night shots!!
When talking about avoiding star trails when shooting stars photography, I mention a “Rule of 500”. And after I did some more research to look into that. I found out that the original is using “Rule of 600”. And the idea is to divide your focal length of your lens by 600 and you will get the number of seconds you can shoot without getting any star trails:
So if you are using a Full Frame body with a 17mm lens:
600 / 17 = 35 sec exposure max.
And if you’re using a crop body, you will need to do a bit more calculation:
1.6 x 17mm = 27.2mm (17mm lens on a 1.6 crop body)
600 / 27.2 mm = 22 second exposure
You don’t have to remember how to do these calculation. Can just follow the table I included last time. Or just like me, only shot between 20 to 30 seconds!! But my point is… Why is some say 500, and some says 600?? So here is another great read about this from Royce Bair. He actually called it “450 Rule” now and have details explanation of why that number has changed over time! And just to give you a hint. It is something to do with prints!
Okay…. so the topic of the post is about “How to shoot star trails?” But we actually spent quite some time talking about how to avoid it…. So before we move on to that. One last goodie I like to share with you is this Clear Sky Chart I recently found. A great tool allowing you to find out if you will get a clear sky at your location, or the place you are going. Check it out!! I am also adding these links under the Tutorials page!
Canon 7D Samyang 8mm, f/3.5, 3955 secs (65minutes) ISO100
So let’s get started! To shoot a star trails photography, there are at least 2 ways that I know of and tried with. But before we get into that, first thing you need to know and possibly buy is a interval/bulb remote controls. There are tons in the market like my first wired remote from Canon, the TC-80N3 for my 7D. It cost me over CAD$200 and last for less than 2 years… Now I’m using some after market brand which cost round $50 or less on some website when order online. Just search for a timer remote for the model of your camera and you should be able to find one for your camera! There are some wireless one as well, which is really good for using outdoor and when shooting long exposure or with extreme focal length lens. And the reason why we need this remote? One is to shoot sequence of images using the interval function. 2nd is to shoot a photo that is over 30 seconds. For most of the DSLR camera, the maximum during of an exposure is only up to 30 seconds in most of the shooting modes. Except the Bulb mode, the one with the letter “B” in the dial. And is the first we are going to look at. All you need to do is to turn your camera to the B mode and your will see your camera display shown Bulb. Now your camera shutter is fully control by the remote. And on the remote, you will also need to set to the Bulb or just B mode. And all you ned to do is to press once to activate to start the exposure, and press the 2nd tie to close the shutter, stop the exposure. That’s is!! If you really not getting this, you might want to find a tutorial online of the remote you got. It’s just not possible for me to have details about that for all types of remotes….
Okay! So one of the 2 ways is just like the photo shown above with the settings: 8mm, f/3.5, 3955 secs (65minutes) ISO100. Remember last post when we talked about shooting the milky way, we used a setting roughly around f/2.8-3.5, 25-30seconds, ISO1600-6400 depending on a lots of factors of course. Things like locations, light pollution, etc. For a star trail photo with a single extremely long exposure shot like this one. 65 minutes exposure. You are really opening the shutter at a very long time letting lights into the lens. And you really have to compensate another side/sides to have a very long exposure without over exposures your image. And you can do that by changing your aperture, and/or the ISO settings. With the image above, I just set the ISO down to 100 and keep the aperture set to max. f/3.5 with the Samyang 8mm lens. This way I can keep the sky exposure correctly over a long period of time. Of course you can bring the ISO higher to give the star trails a bit thicker, stronger. Or if you want to keep the aperture a bit smaller to have more depth in focus. Feel free to experiment with the ISO and aperture. I guess you may already asked the question: “Do I have to stay out for that long? An hour??” And the answer is Yes and No! As you see above, an hour of exposure is giving you a full circle look. And if you actually judge by looking at the longest trails appear in the circle, they are not that long… hey? So if you only exposure for half hour, that half of the length you see. 15 minute will be only a quarter of it’s length, and the circle will not looking like a circle any more…. But likely when you start try taking star trails, you might better off starting with 15 minutes first. Because…. it really does sucks when you are out in the dark, maybe cold and alone, or maybe with someone, but keep asking you if you are done yet every 5 minutes. And after waiting for an hour of exposure, you found out the focus is off. Or someone kicked your tripod in the middle of the wait…. Or the next thing we need to talk about: Have you pointed your camera to frame the rotation of the circle?
When you are looking at the dark sky, how can you find the middle of the rotation take place? Here’s a method I used which told by a friend of mine. And believe is the easiest way. First, you will need to find the most noticeable constellation in the night sky: “The Big Dipper” (as shown below)
After you found it, look for the 2 stars on the right (Merak and Dubhe). And from Merak, try to draw a straight line through Dubhe. After you draw pass Dubhe, keep going until you reach 3 times the distance between Merak and Dubhe. And that point after you reached 3 times the distance of them is roughly the middle point of the rotation of the night sky!! Too confusing?? Here is a animated image to show the rotation with Big Dipper as the cyan lines:
Alright! I think we covered most of the details…. But only on one of the 2 methods. So let’s get into what’s the differences, up side, down side, why to choice one over the others.
The single exposure shot shown above is at Mono Lake in California, a really dark location. The photo does included a little bit of the highway traffic on the left. Where you can have a pretty good idea the amount of lights captured with the traffic over an hour with my camera settings used. Although it wasn’t a lot of traffic going on, still there are quite some cars passed by that night. So if you are in front of an object or building that are barely or well lit up. You will have your foreground object over-exposed for sure!! Single exposure is great since you don’t have to do much. a click and wait for the results after an hour. The down side? Lit up foreground will overly exposed, unwanted airplane or satellite trails, hard to control the results as you have to test one photo for a half hour. Up side? You do have a long time to do light painting to the entire area if you want! Also doesn’t take hundred of shots for the one photos… And I like doing single long exposure like this to empty my battery by the end of it as I usually shooting time lapse sequences with multiple cameras.
So yes! The 2nd way to do star trails photography is to shoot a sequence of photography. And then bring them into your computer and do a process called “Stacking”. Using software to have the multiple shots you took over time, stacking them on top of each other and calculate the differences between each shots and pixels. Putting all the pixels that are different in each photo and stacking them on top to create the trails that you see. And anything that never change within the sequence will leave as the way they were. This will greatly benefit to having a well lit foreground sitting in front of the shot. So how to shoot photo sequence? To shoot photo sequence, you can use different mode with your camera. But I like having a steady exposure shot unless I am capturing some day to night time lapse. So let’s do Manual mode. One good side about using stacking is that you can have your shot well exposure until you happy with it by taking single shot til’ it;s right! Then you can start your interval. If a single shot you took is 12 seconds, you want to set your interval time to at least 15 seconds because you want to give your camera some buffer time. Also have to consider the speed of your memory cards. They might be the reason why your camera waited so long to take another shot. Another reason could also be the in camera noise reduction, make sure you turn that off in the menu!! So set your remote to “INT” interval mode and time to 15 seconds and start your capture. Likely 15 sec interval will have too many photos at the end. If you do want to decrease the amount of photos at the end. 30 sec exposure with 35-40 interval will be a rough number to start with! For the amount of time to capture, an hour for the full star trails circle is still apply under this 2nd method using Stacking.
Alright! so hour later, you collect your photos on to your computer. you will need some software to combine them together creating your star trails shots! And here are a few on both Mac and PC platform. I’m not going to get into these software since I only use one of them on Mac platform.
They are pretty straight forwards to use. Hope it helps you getting your first star trails photo!!
Last thing I want to remind you that with the 2nd method, stacking your shots to do star trails photography. It is not like milky way photo which need a very very dark sky. As long as you have some stars in your single exposure night shots in the sequence, that will be enough to give you star trails after to stack them. And remember that and lights that move in your shots will be adding up together to give you a light trails. That means any moving boats, planes, cars, will be adding together! With this problem, you will not be able to fix if shooting a single shot over an hour. But with Stacking, you can actually go into the photo that have planes, cars in it. And hand clone/painted them out. That way your plane trails will be able to fix. I know that still a bit of work in post. But at least you are not wasting all that time driving to the locations, not to mention to wait at the spot!!!
Again! This will be add to my Resources page!