Going for high dynamic range

Going for high dynamic range
The bright and dark areas of the photo on the left has lost definition while the HDR photos on the right show the details clearly.

In photography, dynamic range refers to the difference between the darkest black and the brightest white. In shutterbug speak, these dark areas in an image are shadows and the bright areas are highlights.

Unlike the human eye, which can perceive the range of contrast and details in a scene, a camera's sensor targets only specific areas in a scene and meters the exposure accordingly.

Ever taken a picture of a friend in front of a brightly lit building? You will have noticed in the resulting photo that your friend's face is underexposed when the details of the architecture are perfect. Or that the building is overexposed when your friend's face looks just right.

Having high dynamic range or HDR reduces the contrast - that is, it lessens the difference between the highlights and shadows, so you can see the details in both the highlights and shadows of a photo.

Remember, an HDR photo is not necessarily a better photo. It just delivers a different effect.

How to use HDR

In the good old days of film, photographers used "dodging and burning" darkroom techniques to increase details in the shadows and highlights in their images.

With digital photography now, photographers take several shots at different exposures and combine them into a picture using software, such as Photoshop or Photomatix Pro, during post-processing.

Your smartphone does the same thing - but in real time. This is why it takes longer to shoot and preview an image using the HDR option.

Many of today's digital cameras have the same HDR option to save you the hassle of post-processing. The Casio Exilim EX-100, among other cameras, even lets you adjust the level of HDR in the picture.

If you feel confident of your skills, you can switch your camera to spot metering. Get exposure readings on the highlights and shadows, then use an exposure that is somewhere in between, and take your photo.

Preview the photo and experiment till you think the photo has precisely the dynamic range you want.

When to use it

It is preferable to use HDR photography in certain situations, as it requires different exposures of the same scene. You can use it, for example, when shooting portraits that are backlit, or that have a high degree of lighting contrast.

But most of the time, HDR photography is best suited for landscapes or architecture, where you will be dealing with plenty of contrast between the sky and the land or building, and where your subjects will be mostly stationary.

Quick tips

The scene should have some contrast in lighting but not too much. If the contrast between the highlights and shadows is too wide, the HDR result can look more like paintings or as some might say, fake.

This might be a bit tricky, as our eyes already perceive the contrast well. But in time, you will know which scene has the right lighting contrast for an HDR shot.

Use a tripod if you can. This is to ensure that when the camera takes multiple shots, it is always shooting the same frame.

In your hands, the camera may move slightly during exposure and this would affect the end result.

It is also not advisable to shoot a scene with movement. If you use your camera's automatic HDR function to shoot a busy street with plenty of passers-by, some of them will be in different positions in the resulting HDR frame.

Finally, practice makes perfect. Do not be afraid to experiment, as you never know what you will get.

trevtan@sph.com.sg

This article was published on Sept 3 in Digital Life, The Straits Times.

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