This article serves as a brief and direct manual solely dedicated to achieving camera focus during nighttime photography with some basic settings to get you started. It deliberately excludes discussions on composition, histograms, or focus stacking. Its sole purpose is to offer a rapid and straightforward approach to night-time focusing techniques.
The number one fundamental aspect of shooting the night sky with a DSLR or mirrorless camera is ensuring your camera is precisely focused on the stars. Contrary to what many might believe, achieving this focus isn’t as complicated as perceived. With the right settings and techniques, you to can shoot great night sky photos!
Setting Up Your Camera
Prepare your camera by setting it to full manual mode, including manual focus, and ensure the lens’s vibration reduction or image stabilisation feature is turned off. Opt for the widest aperture your lens allows, typically around f/2.8 or faster, to maximise light intake. Begin with an ISO setting of 1600 to 3200 to amplify star visibility and an exposure time of 10-15 seconds.
The “500 Rule”
The “500 Rule” is a guideline in astrophotography that helps workout the maximum exposure time to prevent star trailing, ensuring sharper images of the night sky. It suggests dividing 500 by your focal length to estimate the maximum duration in seconds before stars start to trail due to the Earth’s rotation. For instance if you’re shooting on a Full Frame camera using a 24mm lens, the calculation would result in a maximum exposure time of approximately 20 seconds (500 ÷ 24 = 20.8).
If you’re shooting on a crop sensor like I am with my Fujifilm XT5 or X100V you have to do one extra step. First you need to know what the crop factor is of your camera, mine is 1.5x. So on my 16mm lens I multiply this by 1.5 which means I’m effectively shooting on a 24mm lens (16 x 1.5 = 24). Then my calculation would be (500 ÷ 24 = 20.8) which means the maximum exposure time I can do is 20 seconds.
Here’s a list of crop factors for some popular cameras:
- Canon APS-C: 1.6x crop factor
- Nikon APS-C (DX format): 1.5x crop factor
- Sony APS-C: 1.5x crop factor
- Fujifilm APS-C: 1.5x crop factor
- Olympus and Panasonic Micro Four Thirds: 2x crop factor
Using this rule generally helps astrophotographers avoid capturing elongated star trails, thereby achieving sharper and clearer images of the celestial scene.
Utilise LiveView and Digital Zoom / Magnify
Turn on your LiveView mode then find the brightest star in the sky and place it right in the middle of the frame. Use the digital zoom function to magnify the view until the star is as big as it can get in liveview. Don’t change the focal length during this process.
Fine-Tuning the Focus
The goal is to ensure stars appear as precise points of light. Zoom in on the brightest star visible and use the manual focus ring on your lens. Adjust the focus until the star starts to shrink and appear smaller. The ideal focus is reached when the star becomes a distinct pinpoint of light, if you go too far the star will start to get bigger again.
- Stable Support: Use a sturdy tripod to eliminate blurring caused by camera shake, especially with longer exposure times.
- Inbuilt Timer: Use your camera’s built in timer (2/5 or 10 seconds) to trigger the shutter and avoid vibrations from manual pressing.
- Minimise Light Pollution: Keep bright lights off if possible and if illumination is required, use a red torch or use the brightness from your phones screen (not torch). This preserves your night vision and prevents unnecessary interference with your shots.
- Adjust to Darkness: Allow your eyes to adapt to the darkness, which typically takes around 10 minutes. This enables better visibility of the night sky and stars.
- Develop Muscle Memory: Master finding buttons on your camera with closed eyes, known as muscle memory. This allows you to make adjustments without relying solely on sight, particularly in low-light conditions.
Practice, patience, and a comprehensive understanding of your equipment will aid in mastering the capture of the night sky’s beauty.