In my last post, we learned how to find the milky way by getting away from the city lights. In this installment, we’ll learn how to photograph it. This article will assume you have a camera that you can work in manual mode, with a basic understanding of how to change exposure settings and a tripod.
Being in a dark sky region for the first time can be an eye opening experience, literally and figuratively, but you may be in for some disappointment if you’re visiting a dark sky because you were inspired by photos of the milky way taken from Earth by an amateur photographer. Typically, photos of the milky way look like CGI creations in a science fiction movie with brilliant dust clouds, speckled with light and colors imperceptible to the eye at night, contrasted by striking veins of black darkness. When you look at the milky way in person, you might mistake it for light clouds in the earth’s atmosphere and wonder why it doesn’t look more like a scene from War of the Worlds.
That’s because our eyes, while impressively adapted to changes in light, are pretty limited at night when compared with technology. A camera’s sensor has the advantage of collecting and accumulating data in the form of light, much like a canvas collects paint. The longer the sensor is exposed to light, the more that can be seen on the final output. Additionally, the camera can receive color information at night, where the cone receptors of the human eye, responsible for color perception as well as making out differences in contrasting light, are greatly impaired at night. This is why the milky way looks so different to the naked eye.
Combating Dew and Fog
One thing you’ll quickly learn after doing astrophotography is that milky way season occurs during an unfortunate time of the year, unless you live in an arid region. If you live in any other area, you are likely going to encounter fog in the air and dew on your lens and camera when trying to shoot at night. There is no way to combat fog, which can completely ruin any attempt at photographing the night sky, but we can try to predict when it will occur. Fog is likely to occur when the relative humidity is 100%. This means the air is at a saturation point with water and can hold no more. Any excess moisture in the air will not be “dissolved” within the air but will precipitate as fog. You can check the weather forecast to find what the humidity levels will be on a given night, but it’s still nearly impossible to predict and if there is 100% humidity, it doesn’t necessarily mean there will be fog. You can apply some common sense too, for instance, there will be a near guarantee of fog if you’re going out on hot summer night after a day of rain.
A 100% relative humidity occurs when the dew point and the temperature are the same. Condensation, or dew, will form on objects that are colder than the dew point. Once water forms on the lens, you’ll have to remove it periodically with a soft microfiber cloth or else call it a night. I don’t try to predict when dew will form on my camera. One technique involves sealing the camera in an air tight zip lock bag and allowing it to reach ambient temperature before pulling it out to begin shooting. However, this rarely seems to work for me because I’m usually shooting while the temperature is still changing. Instead, I take precautions as soon as it starts getting dark, or as soon as I get out of my vehicle by simply stuffing a sock with a couple activated hand warmers and wrapping it around my lens, using a rubber band to hold it on. The lens is never allowed to become cooler than the surrounding air this way and it has always worked for me, though it won’t necessarily keep dew from forming on the camera itself. I’ve shot with an entry level Nikon and a weather sealed Pentax with and without weather sealed lenses and dew has never interfered with the camera components for me, but don’t take this as me saying “it absolutely won’t hurt your camera” because there’s always a risk with water and electronics. You can always put a plastic bag over the camera itself and tie one end around the section where the lens meets the lens hood, they make bags designed for cameras with hand holes as well.
It’s worth mentioning that there are products that are specifically designed to warm the lens using a similar method and they certainly will look better cosmetically than my setup if that is a concern.
Shooting the Milky Way
Now that you know where you’re going, the hard work is over and we can start photographing the milky way. As I’ve mentioned, this post and the terminology used will assume that you have a basic working knowledge of your camera and the exposure triangle (ISO, aperture, shutter speed). If not, there are many excellent tutorials out there. Here is a good starting point: learn the basics of exposure from The Ultimate Beginners Introduction to Exposure from tutsplus, Lifehacker also has an excellent article on the subject that is less dense and might be easier to understand, and Digital Photography School has a great article for getting started in using the manual mode on your camera, though you may want to consult with your camera manufacturer’s specific instructions on how to use manual mode.
With that said here is a list of essential things you will need:
- A camera that can shoot in manual mode (look for the dial, on the camera with different user modes, “M” should be an option)
- A tripod. It doesn’t have to be an expensive one but the more expensive tripods are pricey because they offer more stability and having something that doesn’t move is paramount.
- A wide angle lens with a wide aperture. I would not use a lens longer than 35mm with an aperture range that at least covers f/4.
- A flashlight and/or headlamp. You gotta see what you’re doing.
Additional items, not required but nice to have are:
- A remote shutter. If you don’t have a remote shutter, wired or wireless, you can opt to use the self timer on the camera. Some cameras allow a self timer of up to 10-12 seconds or as little as 2-3 seconds. The longer time you can use the better because you don’t want any shake during exposure from the camera after you touch it. Use mirror lock up on with the remote, waiting a few seconds to activate the shutter after raising the mirror.
- A headlamp with a red light. Our night vision is less sensitive to the wave length of red light so it is less of a disturbance to our night vision.
- LED flashlights with flood light capability and various beam strengths. The foreground will appear dark in your exposure unless you light it up while taking the shot. LED lights with a wide beam are the best because they put out a flatter, more consistent light than incandescent bulbs. Anything will do, usually the lower powered lights are best because the camera will be set up to capture the smallest amount of light, 20-50 lumens can be more than enough. I’ve used cheap $2 pen lights that you buy at the cash register in stores to great effect. Just experiment shining the light on objects briefly during the exposure. If the light is too intense for the exposure, use a see through cloth or plastic bag over the light to dampen the amount of light.
- Black tape or viewfinder cap. Cameras usually are packaged with a cap that you can put over the viewfinder, you may have tossed it aside not knowing what it’s for but if you can find it, use it. Failing that, use black tape to cover the viewfinder. Failing that, you can use anything else you might have with you. I’ve used my hat before, simply throwing it over the viewfinder to block out light. Otherwise, during long exposures, stray light can leak in through the viewfinder and find its way into the sensor, causing the appearance of light streaks on the final picture. If you’re in a completely dark area, no outside lights and no lights on during an exposure, you’ll probably be fine without covering the viewfinder.
After shooting at night a couple times, you’ll learn what works best with your camera and lens combination. There isn’t a one size fits all approach, but once you find something that works, you can generally use the same settings every time you shoot. Attempting to meter the exposure in camera normally will not work in the dark. I will take you through my set up and reasoning as an example so you can apply it to your own camera.
When I’m shooting in a dark sky region with no nearby light sources, I know I can set my Pentax K-3 with Sigma 18-35mm lens at 18mm, ISO 6400, and f/2.8 for an exposure of 15 secs. This works 90% of the time but sometimes I will make small situational dependent adjustments.
How did I arrive at these settings?
My Sigma 18-35mm is my best lens for night photography. I chose 18mm because that’s the widest I can go. Ideally, I would like to go wider than that but I don’t have a non-fisheye lens that fits the bill.
Aperture. The general mantra of night photography is that you want to shoot at an aperture as wide as possible. The wider the aperture, and the longer the shutter is open, the more light that can be collected by the camera sensor. My lens is capable of shooting at f/1.8 but I rarely shoot at night wider than f/2.8 because everything that is too close and far away from the center of frame appears soft. I want a tack sharp foreground and stars. Your mileage may vary but most lenses lose sharpness at the widest apertures, astrophotography is no exception to the rule.
Film Speed/Sensor Sensitivity (ISO). I chose ISO 6400 because this instructs the camera sensor to be more sensitive to light. The trade-off being the addition of noise, or grain, especially in the darker areas of a photo. The higher the ISO, the better you can shoot in low light but the more grainy the photo will appear. Most photographers detest using ISO settings as high as I do. I find that many are reluctant to go above ISO 1600 for the ever pervasive fear of the dreaded noise issue. However, you will be losing out on a lot of detail in the milky way by using lower ISO’s and not taking full advantage of the technology available to you. I never shoot the milky way lower than ISO 3200 and rarely higher than ISO 6400. I’ll talk a bit more later about how to reduce noise, and one day I will dedicate a whole post to the topic of noise, but for now: I say value you the content that your are shooting and resist the urge to fret so much over noise.
Exposure Time. An exposure of 15 seconds was chosen because that is the amount of time I can go before producing star trails, the movement you see in stars due to the rotation of the earth. The wider the focal length used, the more time you can use without seeing star trails in the final image. This is because the closer you are to a moving object (ie a longer focal length), the more its movement will be apparent. If I shoot wider at say, 8mm, I could probably get by with 30 seconds without seeing movement and this would also allow me to shoot at a narrower aperture if needed.
As an alternative approach, you can use the 500/600 rule. Divide the focal length of your lens by 500 (or 600) to come to the max number of seconds you can expose without getting star trails. This approach may require that you use bulb mode for precise exposure timing and be aware of the crop factor of your sensor. For example, my dSLR has a cropped sensor (crop factor 1.5) – it is not a full frame. In order to find the actual working focal length, I have to first multiply my focal length (I’ll use 18mm since that’s what I shoot with) by 1.5. 18mm x 1.5 = 27mm.
Now, to apply the 500 rule. 500/27mm = 18secs. 18 seconds is theoretically the longest time I can expose without getting star trails. However, I prefer to just use my 15 second time because I’m not gaining much with 3 extra seconds and I have to take the extra step of using bulb mode and a separate timer since my camera is not capable of using an exact 18 second shutter timer.
White Balance. White balance – if shooting in RAW, you can use any white balance setting because it can be changed in Lightroom, Photoshop or whatever your preferred editing software without negatively impacting the overall image; in Lightroom and Camera RAW the slider used to adjust this is called “temperature.”
It can still be helpful to use a white balance setting in camera close to the final color that you want to achieve in order to visualize the final image. Most people prefer to use a cooler tone, and this produces a more “natural” color. The tungsten white balance preset or manually setting it around 4500K will work just fine.
Noise Reduction. Turn on all forms of noise reduction, period. This is often debated and I am perplexed why this is even a debate, especially given the rabid concern over noise. Your camera might have two separate forms of noise reduction: Long Exposure Noise Reduction (LENR) and Noise Reduction (NR – also called High ISO NR) – use them both! If your camera does not have LENR, there are techniques in software like Photoshop where you can apply what is called dark frame background subtraction, which does the same thing as LENR. Take an exposure with the lens cap on using the same settings you used in the milky way and use this tutorial to apply it. The dark frame has to be taken right in the same time frame and location as when you shot the milky way and can not be done when you get home because temperature effects how and where noise is applied in the final image. LENR does essentially the same thing. It takes a separate exposure for the same time without actuating the shutter and applies it to the image in order to subtract out the noise caused by varying temperatures surrounding the camera sensor. Because of this, LENR is the only form of noise reduction you may want to turn off if you’re shooting large panoramas that are time sensitive (ie; you don’t want the sky to change much in the amount of time it takes to shoot several frames).
RAW vs JPEG. Shoot in RAW mode; you want the camera to save the files as RAW’s rather than JPEG’s. Night photography is all about collecting information in the form of light and RAW files contain the absolute maximum amount of information that can be retrieved in post processing. JPEG’s contain a compressed level of data, so there is overall less recoverable details in the final image. In most situations, if given the option, never shoot in JPEG. You will get better at editing the more you do it and software is always improving so we may be able to get even more life from our RAW files through the years, another good reason to shoot RAW.
But, there’s just a bit more on camera settings to go over in the next section covering focus.
Focusing the camera in the dark can be tricky, especially when we’re dealing with small, dim points of light in the sky. As such, I felt this deserved a bit more attention so I’m devoting a separate section to focus. Autofocus (AF) needs areas of high contrast to work, and it will likely be worthless in the dark. You can try using AF if there are street lights in the distance, or if the moon is still in the sky.
What you want to achieve for night sky photography is infinity focus. You may have heard the term “focusing to infinity” in photography, which refers to the point where the lens is focused such that everything beyond a certain distance is in focus (a bit different than hyper focal distance as I understand it). The exact distance that you have to be from something while focused on infinity in order for the object to be sharp depends on the lens, but in general for most wide angle lenses it will probably be around 8-12 feet. I’m probably butchering and over-generalizing the technical detail of infinity, but I know what works for me through trail and error. You can try getting behind the math but I find it easier to just get out there and experiment.
Some lenses have a manual focus ring with an infinity marker, if yours doesn’t, skip to the next paragraph. Switch both lens (if it has a toggle switch) and camera over to Manual Focus (MF) and turn the focus ring so that the marker on the lens matches up with the mark on the focus ring. However, you may have to do some fine tuning because infinity isn’t always at the infinity point on the focus ring and may in reality be just before or after it.
The best way to fine tune focus in MF mode is by using live view on the camera’s LCD screen. While using a tripod, point the camera at the brightest star you can see and switch to live view. In live view, zoom in on the star at the highest magnification possible and turn the focus ring until the star appears as a sharp point of light, rather than a blurred white disc, this will be infinity. Every camera will be different, so the way in which you zoom in on live view will vary between manufacturers, some may not have this feature, but it should operate similar to the way you can zoom in and out on previews of photographs to view fine detail by using one of the dials on the camera.
Now that you’re in focus, you absolutely do not want it to change after all the work you did to get to this point. Make sure both the camera and lens are switched to MF mode and, as an extra precaution, you can tape the focus ring so that it doesn’t move while handling the camera.
Up until now, I’ve only discussed the technical aspects of shooting, but editing the results of your shoot will encompass at least 30% of the work. The downside to shooting in RAW is that it leaves the task of processing entirely to the user. Typically, when shooting JPEG’s the camera will apply some level of post processing to your image, depending on the settings used. A RAW file essentially serves as an incomplete canvas for you to fill in the detail and they will often appear a bit flat, with very little contrast and less vibrant colors than what you may have witnessed when you shot the scene. Keep in mind when editing, many people prefer a more “natural” look to the milky way, but it’s a matter of taste. I like to process my images more on the “surreal” side, the camera, by nature, is creating something more surreal than what I saw anyway. Regardless of the subjective nature of editing, there is a fine line that I believe most viewers can agree on between a nicely processed image and an over processed one where detail becomes lost. It is important to maintain a balance. Still, whether you loathe photo editing or not, if you’ve made it this far – you will have to learn some post processing. I will post some examples of my pre and post processed photos at the end so you can see the results that can be achieved.
I won’t go into post processing here but I will provide a guide to some tutorials that I feel are good starting points and provide better explanations than I could. In future posts, I will dedicate some time to talk about specific processing techniques that I have learned to employ and may not be covered anywhere else. You will need Photoshop or Lightroom for these. It’s best to use a combination of both for different reasons. I will make initial exposure adjustments in Lightroom, then work on it further in Photoshop which allows for a greater amount of control, but you can achieve great results using either program alone.
Hands down, this is the best Milky Way editing tutorial I’ve found by Kenneth Brandon. He uses Photoshop for his tutorial.
If you only have Lightroom, Michael Shainblum, who, in my opinion, is one of the best night sky photographers working today, has an excellent tutorial using Lightroom only.
Did I miss anything? Feel free to add your input in the comments section!