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Understanding Dynamic Range

Last week, I wrote an article about exposure bracketing. In the article I mentioned that exposure bracketing can increase the dynamic range of your camera. Looking back, I probably should have written this article explaining what dynamic range is before writing an article on how to increase your camera’s dynamic range.

What is Dynamic Range?

Have you ever snapped a photo and the photograph didn’t capture the scene like you wanted? Maybe the colors weren’t quite right, the shadows were too dark, or the highlights were too bright? Maybe the foreground was perfect, but the sky was blown out? The reason for this disconnect between what you see and what your camera captures is dynamic range.

Dynamic range is the ratio between the largest and smallest values possible; in the case of photography, we are talking about the ratio between the lightest and darkest parts of an image. The human eye has a larger dynamic range than a camera. The best cameras can only capture about half of the range of luminosity as the human eye. This is why you can see a person’s face clearly when they have light behind them, but a camera will only capture the brightness of the light, leaving their face in shadow.

Overcoming Dynamic Range Limitations

As mentioned last week, one way to overcome the shortcomings of your camera’s dynamic range is to use exposure bracketing. With exposure bracketing, you can take several photos of the same scene with different exposure levels. The different exposures can then be combined in photo-editing software to bring details of both the shadows and highlights into the final image, resulting in an HDR, or high-dynamic-range, image.

Another method to overcome dynamic range limitations is to use a graduated neutral density filter when taking the capture. Neutral density filters darken the image to allow for longer exposures. Graduated filters are dark on one side and gradually lighten toward the opposite side. The darker side of the filter is placed over a high-intensity region, like the sky, and the light side is placed over the darker areas, like the foreground. This helps to even out the luminosity across the entire scene. Graduated neutral density filters don’t provide the same amount of correction as exposure bracketing, but they’re useful for shots where the difference between light and dark isn’t as drastic.

Is It Worth It?

You may be asking, “Is all of this worth it?” The answer to that is both simple and complicated: “It depends.” As with anything in life, there comes a point where the amount of effort exceeds the value of the rewards. No matter how much you increase the dynamic range of an image in editing, you will still be limited by the method of displaying the photo. Most computer screens don’t have the same dynamic range as the human eye, and most printers can’t print in the same dynamic range as your computer screen. If you’re planning to print your photograph, an HDR image may not yield the results you see on screen, but it will be better than an image with no correction at all.

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Exposure Bracketing

As a photographer, it can sometimes be difficult to get the correct exposure across your entire scene. I find this especially applies when taking landscape photographs with a bright sky and when taking photographs at night. This is when a technique known as exposure bracketing can be extremely useful. Exposure bracketing can increase the dynamic range of your camera so you don’t lose some of those details that inspired you to take the photograph in the first place.

So what is exposure bracketing? Simply put, it’s when you take a series of photos at different exposure levels, which you can then blend together to increase the dynamic range of the final image. It’s also sometimes known as HDR or exposure blending. Take these three photos for example:

Exposure bracketing example

In the first photo, the details in the building can be clearly seen, while everything else in the shot is extremely dark. In the second photo, the building is slightly blown out and most of the scene is still too dark, but some of the side details are starting to show up. In the third photo, the building is extremely blown out, but the details in the lawn and the underside of the trees are nice and clear. By combining these multiple exposures in Photoshop, I was able to create an image I was really happy with:

"Mount Timpanogos Temple at Night" (2017) by K. Bradley Washburn

Most digital cameras have a built-in function for exposure bracketing. The built-in function will take a series of 3-5 photos, depending on your camera. If more exposures are needed or desired, you can take a set of photos using exposure bracketing, adjust the base exposure, then take another set of photos. The above image was actually created using ten differently exposed photos, layered on top of each other in Photoshop.

Even if your camera doesn’t have a built-in function, you can still use exposure bracketing. Simply set up your camera and manually adjust the exposure between each shot.

Each camera manufacturer treats exposure bracketing differently, so I can’t go into detail on how to use it on your camera. You should consult the user manual for specifics concerning your camera.