This is Part 8 of a 10 part Natural Light Photography Series.

*The histogram is a graph on your camera that visually represents the tones in your image.*

When you’re underwater, exposure can be tricky. Light behaves unpredictably, and the colors you see in the moment might not translate well into your photos. Enter the histogram—a tool that provides instant feedback on your image’s exposure and tonal balance. Mastering the histogram will not only improve your underwater photography but also save you from the heartbreak of discovering poorly exposed images after the dive.

What is a Histogram?

Photographing alligators in Florida presented a unique challenge due to the dark, shadowy areas of their habitat. The limited light resulted in many underexposed images, as reflected in my histogram here. 1/250, f/7.1, ISO 3200

A histogram is a graph on your camera that visually represents the tones in your image:

Left Side: Represents shadows and dark tones.
Right Side: Represents highlights and bright tones.
Middle: Represents midtones and everything in between.

By analyzing your histogram, you can assess whether your image is underexposed (too dark), overexposed (too bright), or perfectly balanced.

Why You Need the Histogram

While your camera’s LCD screen can give you a quick preview of your image, it’s not always accurate. Bright sunlight or underwater glare can make the screen misleading. The histogram, however, provides an objective view of your exposure, allowing you to adjust settings on the spot and avoid guesswork.

How to Use the Histogram Underwater

Check for Clipping:
- If the graph is pushed all the way to the left, you’re losing detail in the shadows.
- If it’s pushed all the way to the right, your highlights are blown out and lack detail.
Aim for Balance:
- A well-exposed image will have tones distributed across the histogram, with no harsh spikes at either end. Keep in mind that the ideal histogram varies depending on your subject and lighting conditions.

We had heavy cloud coverage that caused the light to scatter unpredictably. I photographed this sperm whale under these conditions—slightly underexposed but still well-balanced. The image had some highlights in the water from the sun breaking through the clouds. 1/320, f/9, ISO 320

4. Adjust in Real-Time:

If your histogram shows overexposure, increase your shutter speed, narrow your aperture, or lower your ISO.
For underexposure, do the opposite: decrease shutter speed, open your aperture, or raise your ISO.

Why the Histogram is Critical Underwater

Underwater conditions are dynamic—light can change in an instant due to depth, water clarity, or cloud cover. By checking your histogram regularly during a dive, you can adapt to these changes and ensure your images are consistently well-exposed.

Tips for Mastering the Histogram

At 30 feet deep with the great hammerheads off Bimini, the lighting was ideal, and my settings were dialed in perfectly. As a result, we captured a well-exposed image, which is reflected in my histogram. 1/320, f/10, ISO 400.

Practice on Land: Familiarize yourself with the histogram before heading underwater. Practice reading it in different lighting conditions to understand how your adjustments affect the graph.
Check Exposure Frequently: Make a habit of checking your histogram after each major adjustment to your camera settings.
Use RAW Format: Even with the best histogram practices, minor tweaks may be needed in post-processing. Shooting in RAW gives you more flexibility to adjust exposure and recover details.

Beyond Exposure: Evaluating Tonal Range

The histogram isn’t just about avoiding over- or underexposure—it’s also a tool for evaluating tonal range. A balanced histogram often results in an image with more depth and detail, capturing the full spectrum of light and shadow that makes your underwater subjects come alive.

Coming Next

In the next blog, we’ll discuss post-processing—a vital step in bringing your underwater images to life. Learn how to enhance colors, recover details, and make your photos truly pop. Stay tuned!

THIS IS PART 8 OF A 10 PART SERIES.

PART ONE - Is Natural Light Photography Photography For You?
PART TWO - The Euphotic Zone! Your best friend.
PART THREE - Custom White Balance, Natural Lights Secret Weapon.
PART FOUR - Shutter Speed: Freezing Moments Underwater.
PART FIVE - Aperture: Achieving Sharpness and Depth Underwater
PART SIX - ISO: Balancing Light Sensitivity Underwater
PART SEVEN - Focus Points: Keeping Your Subject Sharp Underwater
PART EIGHT - The Histogram: Your Underwater Photography Lifeline
PART NINE - Post-Processing: Bringing Your Underwater Images to Life.
PART TEN - The Freedom of Natural Light Photography: A Connection to the Wild

This is Part 5 of a 10 part Natural Light Photography Series.

Aperture, or f-stop, is one of the most important settings in underwater photography. It controls the amount of light entering your camera and determines your depth of field—the range of focus in your image. For natural light photography, where light is limited and animals are constantly moving, understanding how to set your aperture is essential for creating sharp, well-composed shots.

My Go-To Aperture Settings

For most of my underwater photography, I stick to an aperture range of f/8 to f/11. These settings provide enough depth of field to keep the entire subject—whether it’s a shark, whale, or dolphin—in focus, even when shooting wide-angle.

Why f/9 is My Preferred Setting:

It ensures critical features, like the eyes, remain sharp.
It gives enough depth of field to account for slight errors in focus, especially when shooting “blind” (holding the camera away from your body to get closer to the subject).

When to Adjust Aperture

Over/Under Shots:
- Setting: f/11 to f/14 (or higher)
- Why: For split shots capturing both underwater and above-water scenes, a smaller aperture ensures both planes are in focus.
Low-Light Conditions:
- Setting: Open the aperture as wide as your lens allows (e.g., f/4 or f/2.8).
- Why: In dim conditions, opening the aperture maximizes the light reaching your sensor, though this reduces depth of field.

*Tiger Shark off Tiger Beach Bahamas, 1/320, f8, ISO 800*

The Challenges of Big Animal Photography

When photographing large, fast-moving animals like sharks and whales, you often can’t look through the viewfinder. Instead, you’re shooting with your arms outstretched to get closer to your subject—a technique often referred to as “shooting blind.”

Every inch matters when using a wide-angle lens like an 8-15mm fisheye, as the best underwater images have minimal blue water between you and the animal.

By using a mid-range aperture like f/9, you can compensate for the challenges of shooting blind, ensuring that key features remain in focus even if your framing isn’t perfect.

A Safety Reminder

While getting close to your subject often leads to the best photos, always prioritize:

Your safety.
The well-being of the animal.
No image is ever worth compromising the trust and safety of wildlife.

Practical Tips for Using Aperture Underwater

Bonito off Baja feeding on a sardine baitball. 1/500, f9, ISO 800

Experiment with Depth of Field: Start with f/9 and adjust based on your subject and lighting conditions. For larger animals, a smaller aperture (f/11) can help ensure the entire subject is sharp.
Pair Aperture with Shutter Speed: Remember, changing your aperture affects the amount of light entering your camera, so adjust your shutter speed and ISO to maintain proper exposure.
Test Your Lens Limits: Practice with your lens to understand how it performs at different apertures. Wide-angle lenses are forgiving but still require attention to detail.

Whale Shark off Baja, Mexico. 1/320, f9, ISO 500

The Magic of Aperture in Natural Light

Aperture settings can make or break your underwater images. With the right adjustments, you can achieve sharp, vibrant photos that showcase the beauty of the underwater world. Whether you’re aiming for a detailed close-up of a shark’s eye or a dramatic over/under shot, understanding aperture is key to capturing the moment.

Coming Next

In the next blog, I’ll tackle ISO—a setting that can make or break your images in varying underwater conditions. Learn how to balance light sensitivity and noise to achieve the perfect exposure. Stay tuned!

THIS IS PART 5 OF A 10 PART SERIES.

PART ONE - Is Natural Light Photography Photography For You?
PART TWO - The Euphotic Zone! Your best friend.
PART THREE - Custom White Balance, Natural Lights Secret Weapon.
PART FOUR - Shutter Speed: Freezing Moments Underwater.
PART FIVE - Aperture: Achieving Sharpness and Depth Underwater
PART SIX - ISO: Balancing Light Sensitivity Underwater
PART SEVEN - Focus Points: Keeping Your Subject Sharp Underwater
PART EIGHT - The Histogram: Your Underwater Photography Lifeline
PART NINE - Post-Processing: Bringing Your Underwater Images to Life.
PART TEN - The Freedom of Natural Light Photography: A Connection to the Wild