How to find focus at night: A simple step-by-step guide

One of the biggest challenges when photographing at night is capturing images that are in sharp focus.  The reason is really pretty simple and should come as no surprise.  Our cameras have a much more difficult time ‘seeing' when it is dark, just like we do.  Depending on how dark it actually is, and the availability of distant light sources, the auto-focus function of your camera may become very difficult if not impossible to use.  However, there are ways to overcome these obstacles and come away with some fantastic night photos.

Finding focus at night isn't as difficult as it may seem.  It just takes a little bit of practice to learn and perfect the techniques that work best.  The following techniques have proven to be effective, depending on the situation, and are discussed in greater detail in this article:

• Auto-focus on a distant object during the day, then turn off auto-focus and lock the focus ring until the night shoot.
• Auto-focus on the moon or a light on the horizon, then turn off auto-focus on the lens or camera.
• Use a flashlight to illuminate an object and auto-focus on it.
• Set the flashlight in the scene some distance from the camera and auto-focus on that.
• Turn off auto-focus and manually focus the lens. 

What is Infinity Focus?

It is important to note that these tips are primarily aimed at nighttime shooting where infinity focus is desired.  Things such as the Milky Way, stars, the moon, or other astronomical objects are far away.  Depth-of-field isn't really a concern here, but knowing that those far away things are in critical focus is.  That is essentially what infinity focus of a lens is, where very far subjects are sharp. Finding infinity focus is a little different on each lens.  Some lenses have a focus scale and even an infinity symbol (∞).  The problem is that the focus rings on most modern lenses don't stop turning when they reach the infinity mark.  Furthermore, infinity focus is often not actually right on the infinity symbol, but is rather somewhere just before reaching that mark on the lens.

 

Infinity Focus vs. Hyperfocal Distance

This discussion could quickly go down a deep, dark ‘rabbit hole'.  Simply put, hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity ‘acceptably sharp'.  This is important in landscape photography, particularly when there is a foreground element relatively close to the camera.  In that situation, we typically want everything from that foreground to the background (infinity) to be sharp.  That distance varies, depending on focal length, aperture, distance to subject, and even sensor size.

The problem with using hyperfocal distance is some situations is that the background isn't as sharp as it should be (or as sharp as we would like).  Infinity focus will help you to achieve that sharpness.  If you are shooting something very far away, and depth of field isn't a concern, focusing to infinity is the best approach.

Where is Infinity Focus?

OK, we've already established that infinity focus on many lenses isn't actually on the infinity symbol on the lens.  To muddy the waters even more, most kit or lower-end lenses don't even have a focus scale or an infinity symbol.  So how is one to find where infinity focus is on a particular lens?  As with most other things in photography, this is going to be much easier if you are intimately familiar with your gear.  Really get to know how each of your lenses works with the camera body that you have.  While out shooting during the day, auto-focus on a very distant object and then note the reading on the focus scale (if your lens has one).  It should be close to that infinity mark.

For lenses without a focus scale (and infinity symbol), switch to Live View, zoom in on very distant object, and manually focus the lens.  If you are focused on something very far away, then the lens should be focused to infinity.  Unfortunately, if your lens does not have a focus scale and the focus ring turns without stopping, this really won't help you to figure out exactly where infinity focus is to come back to it later.  However, the practice of manually focusing will be helpful for those times when auto-focus doesn't work.

Find Focus at Night

Now that some of the technical details are out of the way, let's focus (pun intended) on how to find focus at night.  Remember that this method will work well for getting distant objects in sharp focus.  With this in mind, let's look in more detail at some techniques for finding focus at night.

Auto-focus during the day and lock the focus ring

This method is pretty straightforward, but requires some patience.  Basically, the idea is to auto-focus on a distant object while there is still enough light to do so.  It could be anything, from a tree on the horizon, a mountain that is far away, or a building in the distance.  Once you do this, the lens should be focused to infinity.  Now the trick is to keep it there until it gets dark and you are ready to start shooting.  A common way to do this is to place a piece of gaffer's tape on the lens barrel to keep the focus ring from moving.  Be careful when doing this so that you don't move it when placing the piece of tape.  It is best to do this with the camera on a tripod, so your hands are free.  You will likely need to tripod after the sun goes down anyway.  Also, don't forget to switch the camera or lens to manual focus after doing this so it isn't hunting for focus the next time you press the shutter button.

 

Auto-focus on a distant light source

This method works even when it is dark.  If the moon is out, that is an obvious choice.  Auto-focus on the moon, switch the camera or lens to manual focus, then you are ready to capture sharp images of other distant objects.  Just be sure to not accidentally bump the focus ring.  A piece of gaffer's tape can be used here as well.

If the objective is to capture the Milky Way, hopefully there is no moon in the sky (or it is a New Moon).  In that case, look for a distant house or yard light on the horizon and auto-focus on that.  If the light is bright enough and large enough, your camera should have no problem locking onto it.  Then again, switch the camera or lens to manual focus and consider using gaffer's tape to prevent the focus ring from moving.

 

Use your own light source

When shooting at night, you will need either a flashlight or, more preferably, a headlamp.  A light will not only help you see where you're going and help to set things up, but can also be used as a focusing tool.  There are a couple ways to do this.  If the light is bright enough, you may be able to shine it on a distant object and auto-focus on that.  However, if the light doesn't provide enough illumination, just walk it out into the scene, lay it on the ground or a rock shining back at the camera, and auto-focus right on the light.

 

Use manual focus

If all attempts at using auto-focus fail, or if you simply desire to fine tune focus, then manual focus is always an option.  Simply turn off auto-focus on the lens and/or the camera and use the focus ring on the lens barrel.  A good way to do this is by using Live View and zooming in to the focus point on the LCD screen.  When focusing on a point light source, zoom in as far as possible and slowly turn the focus ring.  The lens is focused when the point of light is at its smallest on the screen.  After getting focused, place a piece of gaffer's tape on the lens to hold the focus ring in place.

Don't Be Afraid of the Dark

Don't be afraid to venture out into the night after the sun goes down.  Shooting at night certainly does present some unique challenges, but it's a great way to really learn how to dial in the exposure settings on your camera.  Focusing at night can be challenging, but with a little effort and some practice, you'll be capturing sharp images in no time.