Night Sky Photography - Summer is here. For a landscape photographer this time of the year means good weather, green forests, flowers, warmer nights and starry night skies. I enjoy heading out for a sunset and staying until the stars come out, and in many cases, staying out until sunrise. Sunsets and sunrises are always a wonderful time to get dramatic landscape photos, while landscape photos with an amazing Milky Way in the sky above can be unique and dramatic.
Night sky photography is a form of photography that seems mystical and magical. To many people night photography appears to be complicated and left only for those with the most acute photography skill, when in fact once you understand just the basics of the exposure triangle - Shutter speed, aperture and Iso - you will realize that all that’s being done to get these dark night sky photos, in most cases, is to get as much light into your camera as possible.
Set your camera on Manual, set up your tripod and let’s get started.
As most photographers know when you use a long exposure you will need a tripod. Your tripod will keep your camera still during the exposure. You will want to insure that no movement takes place at all during the exposure. Another device that helps with this is a shutter release. The shutter release will keep you from moving the camera when you press the button. If you have no shutter release you can usually set your camera timer to take the photo a few seconds after you click the shutter button.
Your exposure setting will need to be extended, in most cases, up to 20 or sometimes 30 seconds. This will depend on how dark the sky is. Remember that the darker the sky, the brighter the stars, therefore a night without a moon will give the best starry sky. The only negative consequence will be less light on your subject or foreground. Many times just a slight sliver of a moon will allow a more defined foreground while still allowing the stars to shine.
Concerning shutter speed, the only consideration that you must have is that the longer the shutter is open the more movement you will detect in the scene. Even in the stars as at some longer focal lengths the stars will streak slightly when you extend the exposure to 30 seconds. These star streaks turn into star trails if allowed to streak long enough, sometimes up to 30 minutes. This method will create amazing surreal images of steaks and circles of light above your subject. To do this requires another method, not explained here, to pull off.
The next thing that one must consider is how the aperture will block or allow light to pass through the lens and into the camera. When light is dim or it’s dark outside you will want to allow as much light through as possible, and to do this you must use a wider more open aperture - A smaller number. Without getting into the math involved just remember that when you open your aperture you will be allowed a quicker shutter and a lower Iso. Both are desirable, which I’ll explain later. A good quality lens will allow an f/2.8 aperture setting.
Next is your Iso setting. What is Iso? You know that the longer that you keep your shutter open the more light will pass through the lens and into the camera. We also know that an aperture that’s open wider allows more light in. In digital photography we have no film but we do have electronic film in the form of the image sensor. The image sensor’s sensitivity to light can be adjusted. The higher the Iso number the more sensitive to light your camera becomes. Iso 1000 will be more sensitive to light than Iso 100, for instance. Therefor you will need to raise your Iso to get your starry night photos. It’s easy to think that all one needs to do is raise their Iso, but there are negative effects in the form of noise in the image. In film it’s called grain. To get a cleaner image you want to keep your Iso as low as possible. Extending your shutter speed and opening your Iso allows you to do this.
One thing that one must remember when setting up is that in the dark it’s more difficult, or in many cases impossible to use your light meter to determine your settings. Therefore one must take a couple test shots before they get the exposure right.
Another important and in many cases the most difficult part of getting setup for the shot is focus. Unfortunately on a zoom lens when you set the focus to infinity the stars will not be in focus. And at night when it’s dark it’s difficult to manual focus. I recommend taking your camera out in the daylight and setting the focus to an object far away and then marking the lens. I have used tape where when I line up the edges of the tape it’s in focus. There are other methods, but this is the simplest until you gain more experience.
And so once we understand this we can let more light into the camera using these three settings, we can start taking photos in low light. Tripod, long exposure, open aperture and a higher Iso. The next thing to do is to go out and practice. Once you do this a few times your photos will get better and your understanding of what settings to start with will become more second nature.
For more in depth instruction I'm alway available for private one-on-one in field workshops or post processing in person or via Skype.