Intro
Have you ever seen those epic shots where it looks like the stars are streaking across the sky with a perfectly exposed foreground? Wanted to know how they were done? Not only do you need a knowledge of shooting in low light but there are also some relatively advanced post processing techniques involved that will give you the best results.
Equipment
Although there are many challenges that can be over come with technique certain equipment will certainly help you on your way to achieving the results you're after.
CAMERA: A lot of cameras can work but certain types of camera will do a better job than others. To shoot in low light it's always nicer to have a full frame camera capable of shooting at high ISOs and producing low noise images. This doesn't mean it isn't possible on a crop sensor camera, in fact you can still get incredible results but a full frame camera will be better for low light/astro photography.
LENS: A lens with a fast aperture of around F2.8 or below is great, again if you don't have one of these there is no reason why you can't try it out with whatever lens you do have, the lower aperture just helps to capture more light in low light situations.
TRIPOD: Now this is a must, for the technique described below you'll be taking a lot of images and combining these together, if they aren't taken from the exact same spot you'll struggle to accurately blend them together.
TIMER REMOTE: Another must! A timer remote will let you take a lot of long exposures in quick succession. Some cameras have one built in, if not you can buy them relatively cheaply. You'll need to shoot anywhere from 50 to hundreds of images. Not touching your camera in between frames will save you a lot of hassle and result in sharper, more accurate exposures.
HEAD TORCH: I always recommend taking one of these, it will make setting up a lot easier as well as be a useful tool to light paint in certain aspects of your shot.
SOFTWARE: Unfortunately to get the best results you will need to spend some time in editing software. For the image below I used Adobe Photoshop and StarStax. StarStax is a free download and Adobe Photoshop can be picked up as a monthly subscription along with Lightroom both of these are invaluable tools.
The image above is made from around 45 images total; 42 for the star trails and 3 for the foreground, these are combined using software to create the end effect.
Shooting star trails
Once you have all of your equipment together there is a fair amount of technique you’ll need to prepare before hand to make sure you gather the shots you need for the desired end result.
WHERE TO SHOOT: To get nice circular star trails you’ll need to aim towards the North Star, however depending on the effect you need you can experiment and the trails will go from circles to arches depending on which direction you point your camera. The key is not to neglect your foreground though, star trails are cool but an interesting composition goes a long way!
STAR TRAILS: To shoot star trails there are two techniques, the simplest being to use an incredibly long shutter speed. Most DSLRs have a ‘bulb’ mode which, whilst sometimes needing a remote, means you can keep your shutter open for as long as you like. Normally around 30 to 45 minutes will get good trails. However this technique results in hot pixels and noise from the cameras sensor over heating. It also means you have to wait for a long time to to see the results and if your composition or exposure isn’t quite right you have a long time to wait for your next shot!
The second technique is to shoot multiple images and stack them later on. To do this you’ll need to essentially shoot a time-lapse, I find anywhere from 30 to 100 images gives good results, the more frames you shoot the longer your trails will be. If your camera doesn’t have a built in time-lapse function it’s best to use a plug in timer remote. Personally I find 30 second exposures with 0 seconds of interval between shots works well. As you are shooting trails you don’t need to worry about getting sharp stars in each shot, if they streak they will just add on to the next part of the trail.
Some of the frames used for the final stack to create the star trails.
Shooting multiple shorter frames will make it easier for you to expose correctly and compose well. The final stacked result will also make for a much cleaner image. You’ll then have the option of using less or more frames later on to control the length of your star trails.
FOREGROUND: As you are shooting in the middle of the night you may find you want to light paint in your foreground or use different camera settings to get a brighter exposure. For my final image I chose to light paint parts of the image in different stages. To complete my foreground I shot the 3 frames below, I used a mixture of a flash gun and head torch to illuminate certain parts.
Number 1: For this shot I used a flash gun to illuminate the very centre of the cave, this also gave me the best silhouette.
Number 2: From this frame I used another flash gun which illuminated the outer walls of the cave.
Number 3: Here I used a head torch to illuminate the snow in the foreground and the outer rock face.
The edit
STAR TRAILS: Firstly I take all the star trail frames in to Adobe Lightroom and do some basic edits. Remember all we want from these images is the stars so don’t worry about what the foreground looks like, make the stars pop! Once the edit is complete make sure it is applied to all layers. You can do this by either copying the edit from one image and pasting it to the others or simply select all layers before you start your edit. Export all your files as Jpgs in to an appropriately named folder.
Next we need to open up StarStax, a free piece of software that makes this process a lot easier, and upload our images so that it can start the stack.
StarStax on the left with all my frames loaded ready to stack, on the right the compiled stack in one image. This is then exported as a single JPG.
FOREGROUND: As mentioned before the foreground for the final image is a mixture of three images.
The 3 layers are combined using a series of masks and blend modes. The easiest way to blend multiple images where different parts are illuminated is to stack them on top of each other in Photoshop and select the ‘Lighten’ blend mode from the drop down menu. This will mean that only the parts of the image that are lighter than the one below will show. Masks can then be used to fine tune the selection, the opacity slider can be used to control the strength of each light source. Shooting multiple images whilst lighting different areas and blending later can give you more control over your final image. The final foreground result can be seen on the right hand side.
COMBINING THE TWO: Once you have a foreground and a series of star trails you are happy with you can combine the two. You can follow the same steps as blending your foreground but you will most likely find using a mask to do a sky replacement will work best.
This technique does require a little more planning and skill to pull off than a super long exposure but it gives you a lot more flexibility in post and also allows for a much more dynamic and cleaner image.
Once all your layers are combined you can continue your usual edit, for me this is normally contrast adjustments, dust spot removals and colour adjustments.
Anything else you want to know? Any questions in regards to the techniques used above? Let me know in the comments!