Tricks to Enable Autofocus in Conditions of Extremely Low Light

Have you ever found yourself in a situation where the light conditions were so low that your camera was unable to stop autofocusing, with the lens continuously moving back and forth “hunting” to find the focus? I’m sure that you’ve been through this as it’s a fairly common issue. Sometimes, you’d like to capture your beloved in the glow of a candle or snap the image with your little one blowing out candles from the birthday cake.

Perhaps, you’re having a DJ that decides to shut off all the lights on your wedding dance floor, destroying your chances of getting photos that are sharp even if you’re well-equipped with flashes to brighten your subject.

This was exactly what happened to me as well as Lola over the weekend as we were filming a wedding. Lola approached me and asked me if there was something you could suggest to help make autofocus function again. I came up with an idea that works in these kinds of situations.

Autofocus in Low Light
NIKON D3S + 70.0-200.0 mm f/2.8 @ ISO 800, 1/160, f/2.8

The “AF Assist” Speedlight Feature

For this to work it requires an up-to-date speedlight or flash controller with an integrated “AF help” the red beam. A lot of Nikon speedlights such as SB-600, and SB-700. SB-800, SB, SB, and SB-910 are equipped with an AF assist feature and, therefore, any of them can be used. Also, the Nikon SU-800 flash commander will also be able to work (as as long that you don’t require flash for your device).

Focusing in Extremely Low Light

How do you get autofocus to work even in dim light conditions? Here’s a step-by- procedure:

  1. Install a speedlight or commander onto your DSLR camera’s hot shoe.
  2. Change the focus mode to the AF-S (Single Single Area / Servo Focus)
  3. Press the shutter release half-way or button for AF-ON and you will see red light on the speedlight activating
  4. A beam of red light can be projected over your object that will enable your lens to instantly acquire the focus

This technique of focusing is known as “Active autofocus” and relies on what distance is between camera and subject. Since the red beam decreases as distance increases and is only effective on very close subjects that are within 15 feet (which is enough for most scenarios). It’s a far more precise method than that light source, the white “AF Assist” lamp on your DSLR and isn’t restricted to shorter distances, but also has issues with accuracy and is frequently hindered with lens hoods. This is all described in detail on my “autofocus modes explained” article.

This is the way I did it during the wedding. With my Nikon SB-900 speedlight mounted on the camera, I set my focus setting in the AF-S (Single Servo) and then instructed Lola to let the shutter go off immediately after the camera has acquired focus (since there was a lot of dancing and moving constantly). Since the camera cannot continuously monitor subjects when in AF-S mode. Release the shutter once the focus is achieved generally works well.

Unfortunately, there’s no method to track your subject continuously by using the red beam. Therefore, you’ll be limited to AF-S as the only option. If your camera is configured to only shoot only when your subject appears to be focused in AF-S mode then I would suggest changing this setting particularly if you have to focus and compose. For Nikon DSLRs, open “Custom Settings Menu” > “Autofocus” and then set “AF-S prioritization selection” on “Release”. Be aware that once you’ve made this switch the camera will continue to be in AF-S mode even if the subject isn’t in focus.

Wedding Flash Photography #1
NIKON D3S + 70.0-200.0 mm f/2.8 @ ISO 800, 1/80, f/4.0

It is important to note that the red beam of your speedlight for focus can limit the amount of autofocus points that you are able to make use of.

You do not Have to Use Flash

What happens if you don’t wish to utilize flash but nonetheless want to get a precise focus by using the red beam in active use? It’s good to know that you don’t need to. All you have to do is configure your flash to use its AF Assist lamp, and then you can disable flash completely. The problem is that this option is only available for high-end speedlights. Speedlights with lower end capabilities like the Nikon SB-600 and SB-700 do not support this feature.

There are a few solutions to prevent the flash from firing. In addition to setting the flash to its lowest power, and turning the head of the flash forward or preventing it from firing with something, you could follow the directions further below.

Here’s how to disable flash for Nikon SB-900 and SB-910 speedlights. Nikon SB-900 and SB-910 speedlights:

  1. The speedlight should be turned on (ON setting on switch)
  2. Hold and press”OK. “OK” button a few second until Menu opens.
  3. Continue scrolling down the page until you reach the “AF” menu and then click”OK” (under “M ZOOM” and above “STBY”)
  4. Choose “AF Only” and then click OK.
  5. Click the first upper left button to leave the menu.

Here’s a screen shot in the manual for Nikon SB-910, which shows what is known as the “AF only” setting:

Nikon SB-900 SB-910 AF Assist

After this then the flash can only be utilized to assist in autofocus. The flash will not be fired until you modify this setting. The speedlight’s LCD will display “AF-ILL only” as well as the back “ready” lights will switch off.

If you do not want to alter the settings for flash you can find a method to shut off flash however it requires you hold the button continuously in your device. On the majority of Nikon DSLRs, you are able to program buttons (such like the Function button or the AF-L/AE-L buttons) to block flash. This can be done by clicking “Custom Settings Menu” > “Assign the Fn function button” (or you can choose “preview” or “AE-L or AF/L”) and then “Press” and then “Flash off”.

This isn’t the most pleasant method to use for several photographs, as you’d be required to press the programmed button each time you want to shut off flash but there are some who don’t care.

Nikon SB-600 and SB-700 Workarounds

If you own a low-end Nikon flash, such as the SB-600 or SB-700 You can use various methods to disable the flash. The first is to switch the configuration mentioned above by using one of the buttons for functions. In the second step, you can put your SB-600 as well as the SB-700 to commander mode and then shut off the light by turning to the master channel (M) off (double dash).

Wedding Flash Photography #2
NIKON D3S + 50.0 mm f/1.8 @ ISO 400, 1/160, f/2.5

A reader wanted to know how he could observe dancers in dim lighting at short distances, without the use of flash. My suggestion was to apply the technique above, which is extremely effective provided that the dancers aren’t frightened by some light through the speedlight.

I hope that you like the method above We encourage you to give it a go and play around with it.