How To Focus In Low Light For Impressive Blue Hour, Night, And Astrophotography


Learning how to focus in low light is honestly difficult, but here are some tips to get you started.

Some of the most striking images we see are ones taken in the hours of darkness. Blue hour, night and astrophotography are all genres that produce beautiful images, shots that we aspire to take ourselves.

With a little knowledge and some practice, all of these genres are perfectly achievable even to relative newcomers to photography. However, one area where even experienced photographers might struggle is with focus.

Even the best autofocus systems struggle in low light. This is mainly because they rely on contrast detection order to bring the lens to the sharpest focus. Today we are going to look at your best options for focussing in low light.

We will break focussing in low light down into three sections:

  1. Urban Low Light Photography
  2. Rural Low Light Photography
  3. Astrophotography. 

1. How To Focus In Low Light In An Urban Setting

For blue hour and night photography in towns and cities, it is often still possible to use autofocus. The key to obtaining focus is the contrast between the bright city lights and the darkness of the surrounding environment. 

Autofocus will still require some input from you however, it’s not a fire and forget situation. Firstly you should have your camera set to a single point autofocus mode. Then you should position that focus point over a bright light point that has a significantly darker surrounding.

You can do this either by moving the camera, locking focus and then returning the camera to its original composition or by moving the focus point using your camera’s joystick or D-Pad. The later is preferable as for most low light photography you will be using a tripod. 

If you are struggling to autofocus even with the city lights, then the next best option is to focus manually. We will look at ways to focus manually in the following sections.

2. How To Focus Your Rural Landscapes In Low Light.

Unlike cities and towns, rural landscapes can cause significant problems for autofocus in low light. This is due to the lack of any sharp contrasts for the focus to lock on to. In these scenarios, you are going to need to focus manually. The problem is, like autofocus, your eyes still need some contrast in order to obtain manual focus. 

One of the best options you have is to use your camera’s live view. Live view will not only give an electronic rendition of the scene in front of you but also it will add focussing aids and the ability to zoom in on an area of the screen to check focus.

In rural areas, there is a good chance that there will be artificial light sources in the distance. There may even be some natural ambient light to lock on to such as the twilight contrasting under distant clouds. 

With your lens set to manual focus and screen in live view, you should rack your lens focus until that area of contrast is sharp and then take it a little beyond. You then slowly rack back to the point where the contrast is at it’s most defined.

The reason for going beyond the focus point is that you might think the image is sharp but in fact, you are not at the sharpest point. 

Doing this in live view means you can employ a couple of focussing aids to help you. The first of these is focus peaking. This is an extremely useful tool often used by filmmakers. It displays a bright primary color on the screen as areas of contrast come into focus. This allows you to get an accurate indication of where the lens is focussing in all but the darkest of scenes. 

The second option is focus zooming. Most live view modes have the ability to zoom the screen to the point where you wish to focus. This magnification is extremely useful in fine tuning focus to the exact required point.

Your camera might lack a live view mode or you might prefer to use an optical viewfinder. In this case, you will still need to use the above technique of looking for areas of contrast. You also need to allow your eyes to adjust to the darkness, by avoiding looking at strong light sources for around 10 minutes. This includes your mobile phone and even the LCD screen of your camera.

Focussing for Astrophotography.

Lastly, we'll look at how to focus in low light for astrophotography, perhaps the most difficult low light genre in which to obtain sharp focus. The obvious reason for this is that except for the stars, we need to avoid any ambient light around us. So how do we focus?

Again the best tool to use is the camera’s live view. We need to use the LCD live view, not the viewfinder as this will give us a larger image to work with. Look for the brightest star in the sky. This might not be the one in the frame but it will be the best option for getting focus. 

Focus your lens on infinity if possible but be aware the infinity mark may not always focus perfectly on infinity. Again rack the focus to and beyond the point where the star exhibits the highest contrast before fine adjusting to perfect focus. Use the LCD magnification to check focus. It may also be wise to bump up the ISO and shoot a test to check focus. This will reduce the chance of spending a significant time on a long exposure to find it is out of focus.

If you are struggling to find a bright enough star, other options are to look for a distant ground-based light source or to focus on the moon if it is available. You can also use a very bright torch or even a laser pen to illuminate a moderately distant subject and set focus to that.

Low light photography can produce very striking and beautiful images. Understanding how to focus in low light is probably the most difficult aspect of these shots. While you might get decent autofocus in urban scenes, in reality, the best option in low light will always be manual focus. With practice and using the tips outlined above, you should soon be taking beautiful and sharp low light photographs. 

More Resources for Low Light and Night Photography 

About Author

Jason has more than 35 years of experience as a professional photographer, videographer and stock shooter. You can get to know him better here.

Leave a Reply

Your email address will not be published. Required fields are marked *