An Introduction to Camera Exposure Modes

By Joseph Tepper

Cameras are smarter than ever. Take a look at the myriad shooting or exposure modes offered—everything from fireworks to sports mode and night portraits. Unfortunately, the sheer number of shooting modes can lead to confusion about which to use and which to ignore. This is especially true for underwater photography.

Here, we break down the shooting modes you need to know for underwater image-making.

Exposure and Shooting Modes

Some of the confusion on this topic stems from the terminology. Some manufacturers use “shooting modes,” while others use “exposure modes.” So what’s the difference?

“Exposure modes” refer to those modes used to control only the triad of settings that determine exposure—aperture, ISO, and shutter speed. There are four exposure modes: Programmed Auto/Program (P), Shutter Priority (S/Tv), Aperture Priority (A/Av), and Manual (M). We’ll break those down a bit later.

Meanwhile, “shooting modes” is a term that casts a wider umbrella in addition to those core exposure modes. This is because some shooting modes alter other settings in addition to exposure, such as burst shooting or white balance. Each camera has its own selection of specialty shooting modes.

Exposure Modes for Underwater Photography

Exposure modes balance the control over exposure settings between the shooter and the camera. For example, in Manual mode (M) the photographer has complete control over all exposure controls. In Shutter Priority mode (S/Tv), the photographer sets the shutter speed and the camera matches the aperture to produce the proper exposure.

Before we go into depth on each of these modes, you may want to refresh your camera exposure knowledge with our “Taking Control of Your Images with Manual Settings” article from the Getting Started section.

Control Comparison for the Different Modes:

Program Mode for Underwater Photography

In Program mode (labeled “P”), the camera chooses both the shutter speed and aperture, leaving other less essential settings to your control. It is often thought of as the “intelligent auto mode,” because it does most of the work while letting the photographer fine-tune certain settings like ISO, color space, and autofocus.

If you’re still shooting in full automatic mode (see our tips on taking the leap to manual mode) then you should try switching to Program mode. If you don’t want to bother playing with the shutter speed and aperture, at least you’ll have control over ISO. A camera might not know what ISO it can operate at without producing unacceptable digital noise—but you do. So set your ISO and let the camera do the rest.

Most newer cameras also feature “Program Shift.” In this mode, the camera still matches the shutter speed to aperture, but the photographer is able to shift either of the settings, with the camera matching the other setting accordingly. So, for example, if the camera is exposing a scene at 1/125s and f/6.3 and the subject is just a bit blurry, you can increase the shutter speed to 1/250s and the camera will automatically compensate with a more open aperture of f/4.5.

Using Program mode allows you to select certain settings while the camera handles the aperture and shutter speed. Here, selecting fill flash is used to light up a frogfish when the Auto mode might have chosen no flash (Program mode with fill flash)

Alternatively, if using strobes, Program mode gives the photographer some selective control over settings like white balance, which is key for a colorful image

You can also use Program mode to turn off the flash settings when not appropriate, such as taking large, naturally lit images like this shipwreck

Shutter Priority Mode for Underwater Photography

In Shutter Priority mode, the photographer selects the shutter speed and the camera determines the appropriate aperture. Shutter priority is marked either “S” (Nikon, Olympus, and Sony) or “Tv” (Canon).

Because changing the aperture without the photographer’s control impacts the depth of field as well as the amount of strobe light hitting the camera’s sensor, Shutter Priority mode isn’t traditionally used for typical underwater photography situations.

However, it can be useful when photographing fast subjects in natural light. For example, let’s say you’re swimming at the surface with speedy dolphins. You’ll want a fast shutter speed to freeze the mammals’ motion, so you set the shutter speed to 1/1000s. Then, the camera controls the aperture for the proper exposure if lighting conditions change—say some clouds pass by.

Speedy dolphins require a fast shutter speed to freeze their motion. A photographer can set the shutter speed needed to accomplish this while the camera alters the aperture as lighting conditions change slightly (Settings: f/7.1, 1/500s, ISO 400)

Shutter Priority is most often used at the surface or in natural light with fast-moving subjects, like this great white shark (Settings: f/8, 1/250s, ISO 500)

By using Shutter Priority, the camera chooses the appropriate aperture based on your required shutter speed, producing well-exposed black and white images (Settings: f/8, 1/200s, ISO 500)

Aperture Priority Mode for Underwater Photography

In Aperture Priority mode, the photographer selects the desired aperture and the camera determines the proper shutter speed to accurately expose the image. Aperture Priority is either denoted “A“ or “Av” on your dial.

Shooting in Aperture Priority is a popular alternative to full manual mode, especially when shooting wide-angle subjects like schooling fish, seascapes and big animals. The reason for this is twofold: First, it allows the photographer to select the desired aperture, which determines the depth of field in an image. Second, it doesn’t impact the foreground exposure from your strobes since changing shutter speed doesn’t alter the amount of strobe light hitting the sensor. That means you can focus on strobe positioning and composition while your camera alters the shutter speed to accommodate changing lighting conditions.

Most often, Aperture Priority can be used to photograph blurred backgrounds. By setting a low aperture value (f/4–f/8) your camera compensates with a fast shutter speed automatically (Settings: f/5, 1/255s, ISO 400)

The ability to set your aperture needed for proper depth of field and then for your camera to determine the shutter speed is useful when lighting conditions change. Mandarinfish begin mating at sunset, but this quickly turns to night (Settings: f/16, 1/60s, ISO 400)

Finally, consider using Aperture Priority for over-unders. For such images, you require a high aperture value (f/11–f/16) to make sure both the topside and underwater parts of the image are in focus (Settings: f/11, 1/100s, ISO 400)

Manual Mode for Underwater Photography

Manual mode (labeled “M”) requires the photographer to control all elements of composition—shutter speed, aperture and ISO. This is the bread and butter of advanced amateurs and professional underwater photographers, as it allows for the most creativity. When using strobes to light a foreground subject, fast shutter speeds and closed apertures can create a stark black background during the day. Or you can use a shallow aperture to create blur in the background of a macro image.

Unlike other modes in which the camera does part of the work, Manual mode requires the photographer to determine all exposure settings. You will need to use the camera’s built-in light meter to determine the proper combination of shutter speed, aperture and ISO. For this reason, it can be a little bit intimidating and time consuming, especially for the beginning photographer.

However, what you'll quickly learn from using the “semi-automatic” modes listed above is that, while convenient, they can limit creativity. Balancing the ambient light and your strobe output for a complex wide-angle scene is no easy task, and something your camera’s algorithms weren’t built to handle. Also, if you want to experiment with advanced lighting techniques (black backgrounds, backlighting, snooting, motion blur, etc.) then the only way to fully take control of your camera is through the Manual mode.

Manual mode is most useful for lighting and exposing complex scene. Here, you have a strobe illuminating the foreground, lots of backscatter to watch out for, and an off-camera light in the cockpit (Settings: f/5.6, 1/160s, ISO 400)

The real benefits of Manual mode come when you want to experiment with creative techniques. Here, both a fast shutter speed and a small aperture have been used to create a detailed image of a skeleton shrimp framed against a black background (Settings: f/14, 1/250s, ISO 320)

Manual mode allows creativity with light: Here, combining a slow shutter speed with small aperture and mid-strobe power is used to produce a blur effect (Settings: f/14, 1/5s, ISO 400)

Final Thoughts

Cameras have come a long way when it comes to making automatic adjustments—but underwater these automatic settings don’t tend to work well. Having full control over aperture, shutter speed, and ISO is key to properly exposing images. While Manual mode will be the go-to exposure mode for experienced shooters, it is also important to understand the situations where Aperture Priority or Shutter Priority may be useful. And if you don’t feel like micro-managing each individual setting, Program mode is a better alternative than going fully automatic.