What Is Bulb Mode a7III?

What Is Bulb Mode a7III featured photo

If you want to take pictures of the night sky or any low-light situations, you know it can be difficult with a Sony a7III. While the camera has a full-frame sensor, it can only let in a limited amount of light, depending on the shutter speed. Fortunately, using bulb mode can help you capture photos even in pitch-dark environments.

The bulb mode in the Sony a7III allows you to set the shutter speed for 30 seconds or longer. The open shutter enables light to hit the camera sensor until you stop pressing the shutter button. As such, this shooting mode is useful for many low-light conditions. 

Below, we will enumerate the situations where you can use bulb mode. We will also teach you how to use this mode on your Sony camera. But first, let us cover the definition of bulb mode.

What Is Bulb Mode On The Sony a7III?

Bulb mode, or simply B, is a manual shutter speed setting. It allows you to set the shutter speed beyond the standard limit of your camera, which is 30 seconds on the Sony a7III.

With bulb mode, the shutter is open for 30 seconds or as long as you are pushing down the shutter button. Once you release the shutter, the Sony camera takes a picture.

There is no strict limit for Bulb exposure times. You can use this setting for as long as you like, until your battery dies, or the camera overheats, whichever happens first.

Bulb mode offers several advantages to photographers. The longer exposure time enables you to take pictures of low-light scenes. It also helps you achieve creative effects and unique perspectives.

However, using longer shutter speeds might lead to the Sony a7III camera overheating. It can also result in increased noise levels in the long exposure images. Fortunately, the camera automatically reduces noise after shooting. But this step would take the same amount of time the shutter was open, so you cannot take pictures during noise reduction.

When To Use Bulb Mode?

Now that you know the definition of bulb mode, you might be curious about when to use it. Below are several scenarios where bulb mode can help you capture high image quality.

Low-Light Situations

Bulb mode is great for low-light shooting conditions. For example, it helps when taking a picture of a man in a dark alley or a building at night.

Keeping the camera shutter open for 30 seconds or longer help you gather a lot of light. That light hits the sensor, allowing your subjects to take shape and be distinct in the frame.  


Using bulb mode is also recommended for astrophotography. It is a special type of photography that involves taking pictures of celestial bodies. 

The longer exposure time lets you capture the moon, stars, and even distant planets (on certain astronomical events). And if you set an exposure of 20 minutes and more, you can shoot beautiful star trails. This phenomenon is possible because the Earth rotates and stars change their position in the sky.

Light Trails or Painting

Light Trails or Painting

Bulb mode can help you capture light trails, mainly from moving vehicles. It lets you keep the shutter open for 30 seconds or longer. Start experimenting by opening the shutter for around 10 to 15 seconds. If you want a longer light trail, set a longer exposure time.

bulb mode a7iii

With bulb mode, you can also seemingly “paint” light. You can set the exposure time to 30 seconds or more. During that period, you switch on a continuous light, such as a mini LED. Ensure the light is facing the camera. Then, move the light to draw or paint whatever shape you want. After 30 seconds or the pre-determined exposure time, the camera captures the light and whichever direction it took.



You can also use bulb shooting mode when photographing firework displays. It makes the light appear more vivid and grander, resulting in a more magical scene. At the same time, bulb mode lets you capture the entire fireworks show by simply using a longer exposure time. The result is different lights coming together to appear in the final image. 

Long Exposure

Finally, you can use bulb mode whenever you need to capture long exposure photography. For example, when taking pictures of a waterfall, set a long exposure to emphasize smooth motion. You can also switch to bulb mode when shooting lightning. Since it is difficult to predict when lightning strikes, you can simply open the shutter for as long as possible during rainy weather.

How To Find Bulb Mode On The a7III?

You can find the bulb mode on the Sony a7III by setting the top mode dial to M or manual exposure.

Next, turn the rear dial in a clockwise direction until you find the “Bulb” setting.

Adjust the aperture value or f-stops by turning the front dial of the camera.

Then, press the shutter button halfway to prompt the camera to find focus.

Finally, click the shutter and hold it for as long as you need to. The shutter remains open to let light inside the sensor until you release the shutter button.

Note that you cannot use bulb mode when you are using the following Sony camera settings:

  • Auto HDR
  • Rich-tone mono picture effect
  • Silent shooting
  • Certain drive modes (continuous shooting, self-timer, and continuous bracket)

The exposure time limit would be automatically set to 30 seconds.

What Equipment Do I Need For Bulb Mode Shooting?

While you can press and hold the shutter for 30 seconds, it can be difficult if you want a longer exposure time. It would be impractical (and tiring!) to click the shutter for several minutes. Plus, you want to avoid shooting handheld because that leads to a blurry picture. That is why you must invest in the proper types of equipment when using bulb mode.

The first thing you need is a tripod. Choose one made with high-quality material to ensure durability when used daily or outdoors. Having a tripod will prevent camera shake during long exposures. Note that when your shutter is open, the camera captures all movement. It can emphasize even the tiniest motion. So, we recommend mounting your Sony a7III on a tripod.

A wireless remote trigger is another equipment to buy for bulb mode shooting. It allows you to remotely press the shutter button without touching it physically. As such, a remote shutter release reduces the risk of camera shake caused by your hands. 

Although not required, you can also consider an intervalometer when using bulb mode on Sony cameras. This tool lets you control the time interval between shots and the number of pictures to be taken. It is useful for timelapse sequences and long-exposure series.

How To Calculate Exposure In Bulb Mode Using The a7III?

Shooting in bulb mode is quite different from automatic and other camera settings. You usually have the camera to tell you the best exposure time to use. However, during Bulb mode, you must set the parameters yourself, similar to manual mode, which can be overwhelming at first. Fortunately, we will teach you below how to calculate exposure with your Sony a7III camera.

First, set the shutter speed to 30 seconds and ISO to 100. You can adjust the aperture you want to use. Let us take f/16 as an example. This would be your base exposure.

Next, increase the ISO in full stops (meaning ISO 100 becomes ISO 200, and ISO 200 turns to ISO 400). Continue changing the ISO speed until the camera or meter tells you the scene is properly exposed. 

After that, count the increased spots of light. If the difference is three stops (ISO 400), you add the same number of stops to the shutter speed. For example, a 30-second exposure time becomes a two-minute exposure. But if there are only two stops, you let the shutter open for one minute only. 

However, shooting during a cloudy day or from day to evening might be challenging. This is due to light changes within the scene. It might take trial and error to achieve the right exposure with your Sony a7III. Fortunately, you can always use different phone apps to help calculate bulb mode.


The Sony a7III is among the best low-light cameras today. But as a default, it can only take pictures up to 30 seconds. Fortunately, shooting in bulb mode is possible with this mirrorless camera.

Bulb mode is a manual exposure mode setting. It allows you to open the shutter for 30 seconds or longer. It is useful for low-light situations, astrophotography, and other creative photography.

Do you have other questions about the bulb mode on the Sony a7III? Do not hesitate to reach out to us via our contact page!